Enter the child's chronological age and a performance value (percent delay, standard score, or developmental age in months) and the tool checks the child against the four canonical state IDEA Part C eligibility rule families published in the Early Childhood Technical Assistance Center (ECTA 2015) state summary: 25 % delay in one domain, 33 % delay in one domain, 50 % delay in one domain, 1.5 SD below the mean, and 2.0 SD below the mean. Returns Meets / Borderline / Does not meet for each rule along with the margin from the published cut. Built for paediatricians, family-resource coordinators, early interventionists, school-based speech-language pathologists, NICU follow-up clinics, and parents.
Check the child against the four canonical Part C eligibility cuts
Enter the child’s chronological age and a single performance value (percent delay, standard score, or developmental age in months). The tool checks the child against the four canonical state eligibility rule families published in the ECTA 2015 state summary and returns Meets / Borderline / Does not meet for each. Use this to anchor a referral to the state Part C lead agency or to the local IDEA Part B Section 619 preschool special-education child-find team.
Performance input
Enter the published percent delay from the evaluation report.
Enter as a number, not a fraction (e.g. 33 not 0.33)
Enter the chronological age and a performance value to evaluate the child against the four canonical Part C eligibility cuts.
Automate this workflow
Skip the manual count with ConductSpeech
ConductSpeech transcribes the audio, runs the analysis, and writes the clinical report — all in minutes instead of hours.
Paediatric well-child visits when a developmental concern is raised — anchor a single performance value to the four canonical state cut families before making the EI referral
Family-resource coordinator intake at a state Part C office — quick triage of a parent-reported delay before scheduling the formal evaluation
School district child-find intake — quick anchor of a developmental age or standard score against Part B Section 619 preschool eligibility
Speech-language pathologist intake — anchor a PLS-5, REEL-4, or CELF-Preschool-3 standard score to the SD cut families
Early-intervention provider continuing eligibility re-evaluation — confirm the child still meets at least one cut at the annual review
NICU follow-up clinic visits for premature infants and other high-risk medical histories
Developmental paediatrics consultations — quick eligibility anchor before referring to the local Part C office
Parent counselling — translate the developmental test report into a concrete eligibility verdict and a referral pathway
Graduate SLP, paediatric, and early-intervention training — practice mapping a child's performance against the four canonical cut families
Do not use for
As a substitute for the multi-domain developmental evaluation required for the actual eligibility decision — the team must use a state-approved standardised instrument (Bayley-4, BDI-3, MSEL, REEL-4, PLS-5)
For a child whose performance is best described by informed clinical opinion — the calculator does not capture the qualitative case for ICO eligibility
For a child with a diagnosed condition with a high probability of resulting in developmental delay — the child is categorically eligible regardless of the quantitative cut
For monolingual scoring of bilingual children — bilingual children must be evaluated in both languages or in their dominant home language and the standard-score input mode systematically under-estimates bilingual children when applied to an English-only test
As a state-specific eligibility determination — every state has its own published rule and the tool surfaces the four canonical families so the clinician can match the child's value to the locally applicable rule
For children over age 5 who are entering kindergarten — use a school-age IEP eligibility process under IDEA Part B (not Section 619)
Show all four cut families side-by-side
No single national Part C eligibility cut exists. Roughly a third of U.S. states use the 25 % rule, a third use the 33 % rule, a sixth use the 50 % rule, and a separate set of states use 1.5 SD or 2.0 SD norm-referenced cuts. Showing all four families side-by-side lets the clinician match the child's performance to the locally applicable rule rather than guessing or hard-coding a single national threshold.
A 3-percentage-point borderline cusp absorbs single-test noise
Developmental tests on infants and toddlers carry roughly 4 - 5 percentage points of standard error in a single 30-minute administration. A 22 % observed delay against a 25 % cut is within measurement error and should be flagged as borderline rather than a hard "Does not meet". The borderline outcome tells the clinician to re-test or to consider an informed-clinical-opinion route rather than refusing the referral.
Document informed clinical opinion explicitly
Federal law (34 CFR 303.321(a)(3)(ii)) guarantees an ICO eligibility route when standardised test data under-represent the child's true developmental risk. ICO is widely under-used because clinicians forget to document the qualitative case explicitly. When ICO is the basis of eligibility, document the medical record review, parent interview, structured observation, and developmental history in writing so the eligibility decision is auditable and defensible.
Categorical eligibility short-circuits the quantitative cut
A child with a diagnosed condition with a high probability of resulting in developmental delay (Down syndrome, fetal alcohol syndrome, significant prematurity, hearing or vision loss, lead poisoning) is categorically eligible regardless of the percent-delay or standard-score result. Refer the child to the state Part C office immediately and skip the wait-for-evaluation step.
Bilingual children need a bilingual evaluator
Standardised norm-referenced developmental tests with English standard scores systematically under-estimate bilingual children. Use a bilingual or dialect-aware evaluator, evaluate the child in BOTH languages (or in the dominant home language), and rely on informed clinical opinion when the English-only standardised data are not representative. Documenting the bilingual exposure in the eligibility paperwork is required under 34 CFR 303.321(a)(5).
Pair every referral with a hearing screen
Mild fluctuating conductive hearing loss from chronic otitis media is one of the most common reversible causes of delayed speech-language milestones and is often missed by the routine paediatric primary-care hearing screen. Every Part C or Section 619 referral should include a paediatric audiology evaluation in addition to the developmental evaluation.
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Method
The calculator implements the four canonical Part C state-eligibility cut families published in (1) Ringwalt S. "Summary Table of States' and Territories' Definitions of / Criteria for IDEA Part C Eligibility." Early Childhood Technical Assistance Center (ECTA), University of North Carolina, Chapel Hill, 2015 (https://ectacenter.org/topics/earlyid/partcelig.asp); (2) Shackelford J. "State and Jurisdictional Eligibility Definitions for Infants and Toddlers with Disabilities under IDEA." NECTAC Notes 21:1-16, 2006; (3) the federal IDEA Part C regulation 34 CFR Part 303 (definitions of "infant or toddler with a disability" at 303.21 and evaluation requirements at 303.321); and (4) the Bright Futures 4th ed. developmental surveillance schedule (Hagan, Shaw, Duncan eds., American Academy of Pediatrics 2017). Three input modes are supported: (a) "percent delay" (the user enters the published percent delay directly), (b) "standard score" (the user enters a norm-referenced standard score on the standard mean-100 SD-15 metric and the tool converts to a z-score with z = (standard score − 100) / 15), and (c) "developmental age in months" (the user enters the age-equivalent and the tool computes the percent delay with the published Part C formula percent delay = (chronological age − developmental age) / chronological age). Each rule is evaluated independently and the result panel returns Meets / Borderline / Does not meet for each. A 3 percentage-point borderline cusp on the percent-delay rules and a 0.2 SD borderline cusp on the SD rules absorb single-test measurement noise consistent with the published standard error of the Bayley-4 and BDI-3 domain composites. The tool is a screening anchor — it does NOT make the eligibility decision and it does NOT capture diagnosed-condition categorical eligibility or informed clinical opinion (34 CFR 303.321(a)(3)(ii)). Always confirm the actual eligibility decision with the state Part C lead agency or with the local IDEA Part B Section 619 preschool special-education child-find team.
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Published
Published 2026-04-06. Calculations support planning and documentation; verify procurement decisions against manufacturer specifications or institutional SOPs.
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How to cite
How to Cite
ConductScience Early Intervention Eligibility Calculator. ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/early-intervention-calculator
Ringwalt S. Summary Table of States' and Territories' Definitions of / Criteria for IDEA Part C Eligibility. Chapel Hill, NC: Early Childhood Technical Assistance Center (ECTA), University of North Carolina; 2015. Available at: https://ectacenter.org/topics/earlyid/partcelig.asp
Shackelford J. State and Jurisdictional Eligibility Definitions for Infants and Toddlers with Disabilities under IDEA. NECTAC Notes. 2006;21:1-16.
Individuals with Disabilities Education Improvement Act of 2004, 20 U.S.C. § 1400 et seq. Part C — Infants and Toddlers with Disabilities. 34 CFR Part 303. Washington, DC: U.S. Department of Education.
Hagan JF, Shaw JS, Duncan PM (eds). Bright Futures: Guidelines for Health Supervision of Infants, Children, and Adolescents. 4th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2017.
Council on Children With Disabilities, Section on Developmental Behavioral Pediatrics, Bright Futures Steering Committee, Medical Home Initiatives for Children With Special Needs Project Advisory Committee. Identifying infants and young children with developmental disorders in the medical home: an algorithm for developmental surveillance and screening. Pediatrics. 2006;118(1):405-420. doi:10.1542/peds.2006-1231
Zubler JM, Wiggins LD, Macias MM, Whitaker TM, Shaw JS, Squires JK, et al. Evidence-Informed Milestones for Developmental Surveillance Tools. Pediatrics. 2022;149(3):e2021052138. doi:10.1542/peds.2021-052138
Bayley N, Aylward GP. Bayley Scales of Infant and Toddler Development. 4th ed. (Bayley-4). Bloomington, MN: NCS Pearson; 2019.
Speech-language delay is the single most common developmental concern in U.S. paediatric primary care. Roughly 1 in 6 children ages 3 - 17 has a developmental disability and roughly 1 in 12 has a communication disorder (NIDCD 2016, CDC 2019). The scientific case for early identification is overwhelming: the earlier the intervention, the larger the treatment effect, the lower the long-term cost to the family and the public system, and the better the long-term language, literacy, social, and behavioural outcomes (Hagan, Shaw, Duncan eds. Bright Futures 4th ed. AAP 2017; Council on Children With Disabilities, Pediatrics 2006).
The federal floor. The Individuals with Disabilities Education Act (IDEA) is the federal civil-rights law that guarantees a free and appropriate public education to every child with a disability. IDEA Part C (Infants and Toddlers with Disabilities) covers ages 0 - 36 months and is delivered through the state Early Intervention programme. IDEA Part B Section 619 (Preschool Grants) covers ages 3 - 5 and is delivered through the local school district child-find team. Both are federally mandated, free, and available regardless of family income, insurance status, or immigration status.
The state cut. Each U.S. state defines its own quantitative eligibility threshold. The Early Childhood Technical Assistance Center (ECTA, University of North Carolina, Chapel Hill) maintains the canonical state-by-state summary at https://ectacenter.org/topics/earlyid/partcelig.asp. Per the ECTA summary and the Shackelford (2006) NECTAC Notes 21 review, the state cuts cluster into four families: 25 % delay in one domain, 33 % delay in one domain, 50 % delay in one domain, and 1.5 SD or 2.0 SD below the mean on a norm-referenced standardised test. This calculator surfaces all four families side-by-side so a clinician anywhere in the country can match the child's performance to the locally applicable rule.
The Percent Delay Formula
The published Part C definition of "percent delay" uses the chronological age and the developmental age (the age-equivalent at which the child is performing on a developmental test). The formula is:
percent delay = (chronological age − developmental age) ÷ chronological age
A 24-month-old performing at 18 months has a 25 % delay ((24 − 18) / 24 = 0.25). A 36-month-old performing at 24 months has a 33 % delay ((36 − 24) / 36 = 0.33). A 48-month-old performing at 24 months has a 50 % delay.
Most norm-referenced developmental tests (Bayley-4, BDI-3, MSEL, REEL-4, PLS-5) report both a standard score and an age-equivalent — clinicians use the age-equivalent for the percent-delay rule families and the standard score for the SD-cut rule families. The two are correlated but not identical: a child with a 25 % delay on the age-equivalent metric will not always have a standard score below 78. The ECTA 2015 state summary notes that some states accept either rule and some accept only one, and a single child can therefore be eligible under one cut and ineligible under another.
The Standard Deviation Cuts (1.5 SD and 2.0 SD)
The standard-deviation cuts are the second most common state Part C eligibility rule family. The cuts use the standard mean-100 SD-15 metric of norm-referenced developmental tests:
1.5 SD below the mean = standard score ≤ 78 = z-score ≤ -1.5. This corresponds to roughly the 7th percentile and is the most common SD-based cut on the ECTA 2015 summary. States using this cut include New York, Maryland, Connecticut, and Illinois (among others).
2.0 SD below the mean = standard score ≤ 70 = z-score ≤ -2.0. This corresponds to roughly the 2nd percentile and is the most restrictive cut. A small number of states use it as a single-domain cut paired with a 1.5 SD cut in two domains.
Both cuts are computed automatically by the calculator when the user picks the "standard score" input mode. The tool converts the standard score to a z-score with the formula z = (standard score − 100) / 15 and checks the value against the -1.5 and -2.0 thresholds with a 0.2 SD borderline cusp on each rule (matching the published standard error of measurement for the Bayley-4 and the BDI-3 domain composites).
Diagnosed Conditions and Informed Clinical Opinion
Two important non-quantitative eligibility routes exist on top of the percent-delay and SD cuts.
Categorical eligibility for diagnosed conditions. A child with a diagnosed condition with a "high probability of resulting in developmental delay" is categorically eligible for Part C without a quantitative test (34 CFR 303.21). The federal regulation lists examples: chromosomal abnormalities (Down syndrome, Trisomy 18, Fragile X), congenital genetic disorders (cerebral palsy, spina bifida), congenital infections, sensory impairments, inborn errors of metabolism, fetal alcohol syndrome, significant prematurity (typically < 32 weeks gestation or < 1500 g), and lead poisoning. Each state publishes its own list of categorically eligible conditions on top of this federal floor — the ECTA Center maintains the state-by-state comparison.
Informed clinical opinion (ICO). Every state Part C programme MUST accept informed clinical opinion as an eligibility category (34 CFR 303.321(a)(3)(ii)). ICO applies when standardised test data under-represent the child's true developmental risk: a child who is too young, too dysregulated, too ill, or too unfamiliar with the examiner to be tested validly; a child with a complex medical history; a child with strong family-history risk; or a child whose performance varies widely between settings. ICO is the multi-disciplinary team's qualitative judgment based on review of the medical record, parent interview, structured observation, and developmental history. ICO eligibility documentation should be detailed and explicit so the eligibility decision is auditable.
A "Does not meet" verdict in the calculator does NOT rule out eligibility — the child may still qualify under either of these two routes. Always confirm the actual eligibility decision with the state Part C lead agency.
Frequently asked
What is this calculator for?
This is a free, client-side eligibility screener for Early Intervention (IDEA Part C, ages 0 - 36 months) and the IDEA Part B Section 619 preschool special-education programme (ages 3 - 5). Enter the child's chronological age and a single performance value (percent delay, standard score on a norm-referenced developmental test, or a developmental age in months) and the tool checks the child against the four canonical state eligibility rule families published in the Early Childhood Technical Assistance Center (ECTA 2015) state summary. The result panel returns Meets / Borderline / Does not meet for each rule along with the margin from the published cut. Use the result to anchor a referral conversation with the state Part C lead agency or with the local school district child-find team — every state has its own published rule and the tool surfaces the four canonical cuts so the clinician can match the child's performance to the locally applicable rule. The tool is NOT a state-specific eligibility determination — always confirm the actual eligibility decision with the state Part C lead agency.
What are the four canonical Part C eligibility cut families?
Per Shackelford (2006) NECTAC Notes 21 and the Early Childhood Technical Assistance Center 2015 state summary, U.S. Part C state eligibility cuts cluster into four families. (1) 25 % delay in one developmental domain (the most permissive cut, used in roughly a third of states). (2) 33 % delay in one domain or 25 % delay in two or more domains (the modal U.S. cut and the most common state-level rule on the ECTA 2015 summary). (3) 50 % delay in one domain or 25 % in two or more domains (used in roughly a sixth of U.S. states and territories). (4) Standard-deviation cuts: 1.5 SD below the mean (standard score ≤ 78 on a test with mean 100 and SD 15) and 2.0 SD below the mean (standard score ≤ 70). On top of these quantitative cuts every state must offer (a) categorical eligibility for diagnosed conditions with a high probability of resulting in developmental delay (Down syndrome, fetal alcohol syndrome, significant prematurity, hearing loss, vision loss, lead poisoning) and (b) eligibility on informed clinical opinion (34 CFR 303.321(a)(3)(ii)) when standardised test data under-represent the child's true developmental risk.
How do I enter the child's performance value?
Pick the input mode that matches the data you have on the evaluation report. (1) "Percent delay" — enter the published percent delay directly as a number (e.g. 33 for a 33 % delay). This is the most common output from the developmental evaluation report. (2) "Standard score" — enter the standard score from a norm-referenced test (Bayley-4, BDI-3, MSEL, REEL-4, PLS-5, CELF-Preschool-3, etc.) on the standard mean-100 SD-15 metric. The tool converts the score to a z-score and checks the SD cuts. (3) "Developmental age" — enter the age-equivalent in months reported by a developmental test and the tool computes the percent delay using the published Part C formula: percent delay = (chronological age − developmental age) / chronological age. A 24-month-old performing at 18 months has a 25 % delay.
Why does the tool show four rules side-by-side instead of one?
Because state Part C eligibility rules vary widely and a single national cut does not exist. Per the ECTA 2015 state summary, roughly a third of U.S. states use the 25 % rule, the modal U.S. cut is the 33 % rule (used in roughly a third of states), a sixth of states use the 50 % cut, and a separate set of states use 1.5 SD or 2.0 SD norm-referenced cuts. Showing all four cuts side-by-side lets the clinician see which rules the child meets and match the result to the locally applicable rule. Borderline outcomes flag children whose performance falls within measurement error of the cut so the clinician knows when a re-test or an informed-clinical-opinion route is warranted.
What is "informed clinical opinion" and when does it apply?
Informed clinical opinion (ICO) is a federally mandated eligibility route under 34 CFR 303.321(a)(3)(ii) — every U.S. state Part C programme must accept ICO as an eligibility category alongside the quantitative cut. ICO applies when standardised test data under-represent the child's true developmental risk: a child who is too young, too dysregulated, too ill, or too unfamiliar with the examiner to be tested validly; a child with a complex medical history; a child with strong family-history risk; or a child whose performance varies widely between settings. ICO does not require a percent delay or a standard score below the cut — it relies on the qualitative judgment of the multi-disciplinary evaluation team. Document the ICO basis explicitly in the eligibility paperwork: the team's review of the medical record, the parent interview, the structured observation, and the developmental history all count.
What is "categorical eligibility" for diagnosed conditions?
A child with a diagnosed condition with a high probability of resulting in developmental delay is categorically eligible for Part C — no quantitative test or percent-delay cut is required. The federal IDEA Part C regulation (34 CFR 303.21) lists examples: chromosomal abnormalities (Down syndrome, Trisomy 18, Fragile X), genetic or congenital disorders (cerebral palsy, spina bifida), congenital infections, sensory impairments (severe visual or hearing loss), inborn errors of metabolism, FAS / FASD, significant prematurity (typically born at < 32 weeks gestation or < 1500 g), severe attachment disorders, and exposure to lead. Each state publishes its own list of categorically eligible conditions on top of the federal floor — the ECTA Center keeps a state-by-state comparison. A child with a diagnosed condition is referred to Part C immediately and the eligibility paperwork is processed without a developmental evaluation as the gating step.
What's the difference between Part C and Part B Section 619?
Both are sub-parts of the Individuals with Disabilities Education Act (IDEA) and both are federal programmes administered through the states. IDEA Part C — Infants and Toddlers with Disabilities — covers children from birth through age 3 (the day before the third birthday). Part C services are delivered through the state Early Intervention programme (the state lead agency varies by state — sometimes the Department of Health, sometimes Education, sometimes Disabilities). Services are free, no parent referral is required, the evaluation is at home or in a community setting, and the family receives an Individualised Family Service Plan (IFSP). IDEA Part B Section 619 — Preschool Grants — covers children ages 3 through 5 (until kindergarten entry). Part B Section 619 services are delivered through the local school district child-find office and the school district special-education team. Services are still free, the evaluation is done by the school district, and the child receives an Individualised Education Programme (IEP) instead of an IFSP. Children transitioning from Part C to Part B Section 619 around their third birthday should be referred to the school district child-find team at least 90 days before the transition (the federal "transition meeting" requirement).
How do I make the actual referral?
For a child under age 3: call the state Early Intervention programme directly. Every U.S. state has an EI office and the phone number is on the CDC "Learn the Signs. Act Early." website (https://www.cdc.gov/ncbddd/actearly/parents/states.html). A paediatrician referral is helpful but is NOT required — federal law guarantees that any caregiver, family member, social worker, or community member can make the referral. The EI evaluator will come to the home within 45 days of the referral and will run a multi-domain developmental evaluation. For a child age 3 - 5: contact the local school district child-find office. Every U.S. school district has one and it is legally required to evaluate any child age 3+ with a suspected delay regardless of whether the child attends a public preschool. The evaluation is done by the school-district special-education team, services are free, and the child receives an IEP at the preschool. For both pathways: pair the referral with a paediatric audiology hearing evaluation because mild fluctuating conductive hearing loss from otitis media is one of the most common reversible causes of speech-language delay.
Is the tool a substitute for a Part C evaluation?
No. The tool is a quick eligibility screener that maps a single performance value to the canonical state cut families — it is not a standardised developmental evaluation and it does not produce an IFSP or an IEP. A Part C eligibility decision requires a multi-domain developmental evaluation by a qualified team using a state-approved instrument (Bayley-4, BDI-3, MSEL, etc.), parent interview, structured observation, and review of the medical record. Use this tool to decide whether to make the referral, not to make the eligibility determination itself.
Is the tool appropriate for bilingual children?
Yes, with caveats. Bilingual children must be evaluated in both languages or in their dominant home language under 34 CFR 303.321(a)(5) and 34 CFR 300.304(c)(1)(ii). Standardised norm-referenced developmental tests with standard scores assume monolingual American English performance and will systematically under-estimate bilingual children — entering an English-only standard score for a Spanish-dominant 2-year-old is one of the most common false-positive eligibility flags in U.S. paediatric primary care. Use the developmental-age input mode with a bilingual or dialect-aware evaluator, document the bilingual exposure in the eligibility paperwork, and rely on informed clinical opinion when the standardised data under-represent the child's true competence.
Is my data private?
Yes. The calculator runs entirely in your browser. Nothing is sent to a server, nothing is saved, and the values you enter are gone the moment you close the tab. The tool is safe to use at the point of care, in the home visit, in the well-child visit, or by a parent at home.
