Explore the evidence
10 of 88 decisions · clear everything
Early gains fade by default — halving every 12–18 months, faster when bigger. What persists is trajectory (placement, graduation), not ability.
strong supportconf: highgc: lowFadeout — why early gains disappear, and what actually persists · early-childhood · ages 4–18 · structure
Timed retrieval practice builds arithmetic automaticity — beating identical untimed tutoring head-to-head — and the anti-timed-test harm claims have no causal evidence.
strong supportconf: highgc: lowMath-fact fluency and timed practice (and the anti-timed-test claims) · math · ages 5–12
Testing yourself beats rereading — robust in real classrooms; honest durable size ~0.1–0.3 SD, biggest after delay, thinnest on transfer.
strong supportconf: highgc: lowRetrieval practice (the testing effect) · practice · ages 8–18 · method
Spacing beats massing at equal total time — the most robust finding in learning science. Space repetitions at ~10–20% of how long you need to remember.
strong supportconf: highgc: lowSpaced (distributed) practice · practice · ages 6–18 · method
Systematic phonics beats whole language for word reading — largest in K-1 and for at-risk readers; near-null for comprehension and past grade 3.
strong supportconf: highgc: lowSystematic/explicit phonics vs whole language and balanced literacy · reading · ages 4–9
Physical capacity is about as heritable as cognitive ability (~60%, no shared environment). Whether trainability is a stable trait remains unproven — the skeptics are winning.
strong supportconf: highgc: lowTalent and trainability — what is heritable, and what that does not license · talent · ages 4–18 · input
Teacher quality is the largest within-school lever — 1 SD of teacher ≈ 0.10–0.15 SD/yr, worth more than ten fewer students — and credentials predict none of it. Select; don't workshop.
strong supportconf: highgc: lowTeacher quality — selection over credentials and workshops · teachers · ages 4–18 · structure
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: lowTutoring — the honest effect, the Bloom 2-sigma myth, and what survives scale · tutoring · ages 5–18 · method
Later bells buy adolescents 40+ measured minutes of sleep — the best-identified positive effect in the archive; the achievement payoff is real but far smaller.
strong supportconf: mediumgc: lowDo later school start times increase adolescent sleep, and does that raise achievement? · health · ages 11–18 · input
Teaching grammar does not improve writing at any age tested — and it displaces the things that do.
negativeconf: mediumgc: lowDoes teaching grammar improve children's writing? · writing · ages 5–18
The URL is the state — any view you build here is a permalink you can hand to someone mid-argument.