The Evidence on Teaching

Explore the evidence

7 of 88 decisions · clear everything

Survives the gold standardIndependent, durable, rigorousThe debunked shelfCheap winsFor parents at homeFamous numbers, deflatedWhere we admit ignoranceThe terrain
evidencealldrop DA–BA only
evaluatoranyno dev-ledindependent
durabilityanyfollow-up≥1yr≥2yr
what are these? →
sortconfidencerobustfragileA–Z
domain
verdict
confidence
layer
survival prior
Your situation · from the applicability layer — absence means “not yet assessed,” never “doesn’t apply”
who's delivering
group / setting
cost
outcome class

High-dosage tutoring is education's most reliable lever: ~0.29 SD in trials, ~0.2 well-scaled — not Bloom's 2σ. Groups of 3–4 work; 1:1 is unnecessary.

strong supportconf: highgc: low
18/1830/48connected:Class-size reductionDoes educational technology raise The parent as instructorSchool spending, charters, and wha

Tutoring — the honest effect, the Bloom 2-sigma myth, and what survives scale · tutoring · ages 5–18 · method

Smaller classes buy real K-1 gains that fade on tests yet persist in attainment — at roughly triple tutoring's cost, and diluted to nothing when scaled fast.

mixedconf: highgc: low
7/748/48connected:TutoringDoes educational technology raise Teacher quality

Class-size reduction · class-size · ages 4–18 · structure

At scale, pre-K doesn't durably raise test scores — Tennessee went negative — yet Boston shows real attainment gains beside a test-score zero. It buys trajectory, not ability.

mixedconf: highgc: low
17/1748/48connected:FadeoutPerry Preschool and Abecedarian

Preschool at scale — Head Start, state pre-K, and what universal provision delivers · early-childhood · ages 4–5 · structure

The received wisdom that retention is harmful was two measurement errors, not a finding. Fix them and the achievement effect is zero — but the grade at which you hold a child back decides everything.

mixedconf: mediumgc: low
19/1936/48

Grade retention — holding a child back versus promoting, and test-based promotion policies · retention · ages 5–18 · structure

Taking time away hurts measurably; adding it back buys almost nothing. The return per hour is ~0.02-0.03 SD, concave, and near zero in disorderly classrooms.

mixedconf: mediumgc: low
23/2338/48

Length of the school day and year, time-on-task, extended time, and summer · time · ages 4–18 · structure

Perry and Abecedarian: n=123 and n=111, IQ gains gone by adolescence, attainment effects real but multiplicity-fragile. Too thin to carry the policy built on them.

mixedconf: mediumgc: low
8/836/48connected:Preschool at scale

Perry Preschool and Abecedarian — what the famous studies actually establish · early-childhood · ages 4–5 · structure

Coaching buys ~0.25 SD of score and has for 42 years — a fraction of what's advertised — and none of it is ability. The score moves; the construct doesn't.

mixedconf: mediumgc: medium
20/2036/48

Test preparation — does coaching raise scores, and does a raised score mean raised ability? · assessment · ages 5–18 · structure

Not yet assessed for this question · 4

The URL is the state — any view you build here is a permalink you can hand to someone mid-argument.