Where these numbers come from
The briefs name their source in the sentence itself. This page holds the links, so any number can be checked without hunting through the library for it.
The links live here rather than in the briefs on purpose. Paraeducators read the briefs, most of them mid-shift, and a page dotted with long web addresses stops being a tool and starts looking like a journal article. Naming the authority in the sentence is what makes the claim checkable; the address only has to be somewhere findable.
This covers the briefs that have been through the sourcing pass, not the whole library. A brief that is not listed has not been through it yet.
29 claims across 18 briefs.
02.01 — IDEA Overview for Paras
Before EHA, about 1 million U.S. children with disabilities were shut out of public schools
Congress's own findings in IDEA
20 U.S.C. §1400(c) — the statute states the figure about the era it was passed to end
04.05 — Reinforcement Basics
There is no research-backed number for the positive-to-corrective ratio — the direction is supported, the figure is not
Sabey, Charlton and Charlton, Journal of Emotional and Behavioral Disorders 2019
Reviewing the ratio literature directly: the rule has good face validity but lacks empirical support for any specific number. The brief previously stated 4:1 as a research finding.
05.18 — PBIS and the Para's Role
CICO is the most-studied Tier 2 intervention, with mixed rather than uniformly strong support
Maggin and colleagues, Journal of Positive Behavior Interventions 2015
A systematic evidence review; effects vary with behaviour function and implementation fidelity
07.01 — Autism
Autism at about 1 in 31 U.S. children
CDC, Autism and Developmental Disabilities Monitoring Network
2022 surveillance year, published 2025
39.6% of identified autistic children had an intellectual disability
Ranged 31.2%–52.8% depending on the group of children looked at
Epilepsy about 21.5% where intellectual disability is present, about 8% where it is not
Amiet and colleagues, meta-analysis
Pools 10 studies published through 2006
Anxiety and ADHD co-occurrence carry no figure. Published ranges run 0–82% and 0–86%; no authority states a tighter one, so the brief says the conditions co-occur and stops there.
07.02 — ADHD
The 20,000-additional-critical-messages-by-age-10 figure is a clinician's estimate, not a study
Attributed in the popular literature to William Dodson, MD
No peer-reviewed source states it; the brief previously credited it to Russell Barkley's research
07.04 — Dyslexia
About 3–7% at a criterion of 1.5 standard deviations below the mean
Fletcher et al. 2019; Peterson & Pennington 2012; Snowling & Melby-Lervåg 2016
17.4% at a 25th-percentile cut
Dyslexia lasts into adult life
The widely-repeated “5–17%” figure is not the IDA's, though much of the web attributes it there — the IDA's own page gives 15–20% for language-based learning disabilities, a broader category. The brief states the range as what it is: an artefact of where the cut-off is set.
07.05 — Intellectual Disability
IQ about 2 standard deviations below the mean; onset before age 22
American Association on Intellectual and Developmental Disabilities
The before-22 developmental-period rule is AAIDD's 2021 revision, up from 18
07.06 — Emotional Disturbance (EBD)
No research-backed number for the positive-to-corrective ratio
Sabey, Charlton and Charlton, Journal of Emotional and Behavioral Disorders 2019
Good face validity, no empirical support for any specific ratio. The brief previously called 4:1 well-evidenced, crediting Sprick et al.
07.07 — Speech and Language Impairment
About 1% of people stutter
National Institute on Deafness and Other Communication Disorders
07.08 — Down Syndrome
About 1 in 700 U.S. births
Trisomy 21 about 95%, translocation about 3%, mosaicism about 2%
Heart defects from birth 40–50%; some hearing loss about 75%; sleep apnea 50–79%
American Academy of Pediatrics
Health Supervision for Children and Adolescents With Down Syndrome, 2022
The CDC and the National Down Syndrome Society count occurrence differently — 1 in 700 against 1 in 775 as of 2018. Both are current. The brief uses the CDC's and says so rather than silently picking one.
07.09 — Cerebral Palsy
About 1 in 345 children
CDC ADDM cerebral-palsy tracking
2010 surveillance — the most recent the CDC has published
Epilepsy about 42% of identified children
CDC ADDM cerebral-palsy tracking
2010 surveillance
Vision, hearing and speech co-occurrence carry no figures: no US authority states them.
07.11 — Deaf and Hard of Hearing
More than 90% of Deaf children are born to hearing parents
National Institute on Deafness and Other Communication Disorders
07.12 — Visual Impairment
Low vision: acuity 20/70 or poorer, not correctable with regular glasses
Legally blind: 20/200 or less, or a visual field of 20 degrees or less
41% of working-age adults with vision difficulty in paid work, against 72% without
Current Population Survey 2023, via the American Foundation for the Blind
07.14 — Tourette Syndrome
Coprolalia in a minority — roughly 1 to 2 in 10
ADHD about 60%; OCD figures likewise
Tourette Association of America
Both from clinic samples; whole-population rates run markedly lower
The brief says so in the text: a para who expects the clinic rate in a classroom will over-expect.
07.15 — Anxiety Disorders
31.9% of adolescents have had any anxiety disorder
National Institute of Mental Health
Lifetime prevalence, National Comorbidity Survey Adolescent Supplement
This brief previously said “about 1 in 10 by their teens” — an understatement of roughly three times, in the direction that makes a para less likely to expect anxiety in the students in front of them. It had passed a careful human read: a figure is not checkable by reading closely, only by opening the source.
07.18 — Selective Mutism
Around 0.5%–1% of children
School-based and clinic prevalence studies
Published estimates range 0.2%–1.9% by setting and age
07.20 — Fetal Alcohol Spectrum Disorder
1 in 100 to 1 in 20 first-graders
Conservative range across four US communities
Fetal alcohol syndrome can be diagnosed without a confirmed exposure history; partial FAS only under the Revised IOM guideline
Comparison of the five current FASD diagnostic guidelines
The other four guidelines require confirmed exposure for partial FAS
15.07 — Poverty and Schooling
The size of the early vocabulary-exposure gap is disputed
Sperry, Sperry and Miller, Child Development 2019; reply by Golinkoff and colleagues
Five communities; a far smaller gap when all speech heard is counted rather than only child-directed speech. Hart and Risley's original figure rests on 42 families