Explore the evidence
13 of 88 decisions · clear everything
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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
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
Group within classes or across grades by subject: modest, nearly free wins. Whole-school streaming does nothing, and early between-school tracking harms the bottom.
moderate supportconf: highgc: lowAbility grouping and tracking — four practices, four verdicts · grouping · ages 5–18 · structure
Accelerate ready kids: they keep pace with older classmates, bank a year, and show no social-emotional harm at 50. The gifted label itself does nothing; the content does.
moderate supportconf: highgc: mediumAcceleration and gifted programs — the label vs the content · grouping · ages 5–18 · structure
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: lowClass-size reduction · class-size · ages 4–18 · structure
Curriculum is nearly free, so choosing beats not choosing — but the payoff is avoiding a demonstrated loser, not finding a magic winner. Content is the high-upside bet.
mixedconf: highgc: lowCurriculum choice as a school-level lever · curriculum · ages 4–14 · 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: lowPreschool at scale — Head Start, state pre-K, and what universal provision delivers · early-childhood · ages 4–5 · structure
Unallocated money is the worst buy in the database; the same dollars as No-Excuses charters buy +0.3–0.4 SD/yr — and the average charter is a precise null.
mixedconf: highgc: lowSchool spending, charters, and what school-level choices actually move outcomes · school-structure · ages 4–18 · structure
Starting school older mostly manufactures an age-at-test artifact: the IQ effect collapses to ~−0.07 once identified. Real residues: less hyperactivity, unchanged attainment.
mixedconf: highgc: lowSchool starting age, relative age, and academic redshirting · early-childhood · ages 4–7 · structure
Most measured 'home environment' effects are parents' genes: three-quarters of parent-child transmission isn't rearing, and a whole better childhood buys ~4 IQ points.
mixedconf: highgc: lowThe early home environment — what parents can and cannot causally move · early-childhood · ages 4–10 · input
Brain training improves the trained task and nothing else: far transfer to intelligence or achievement is 0.001 against active controls.
no effectconf: highgc: lowDoes working-memory or brain training transfer to intelligence and achievement? · transfer · ages 4–18 · debunked
Matching instruction to 'learning styles' does nothing: real matching experiments return d=.04. The correlational literature IS the myth.
debunkedconf: highgc: lowDoes matching instruction to a child's "learning style" improve learning? · debunked · ages 4–18 · debunked
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