Explore the evidence
35 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
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
Minimal-guidance math trailed every rival in the one multi-curriculum RCT; explicit instruction for strugglers is math's most replicated result.
moderate supportconf: highgc: lowExplicit vs reform/constructivist math instruction · math · ages 5–18
Word-problem solving is its own skill: computation fluency doesn't produce it. Teaching problem schemas explicitly does (~0.25–0.45 SD on trained content).
moderate supportconf: highgc: lowWord problems, schema instruction, and the conceptual-vs-procedural question · math · ages 6–14
Neither acceleration mandates nor delay mandates work — readiness-matched placement does. Push everyone and the median falls; hold everyone back and the top falls.
mixedconf: highgc: lowAlgebra timing — acceleration mandates, delay mandates, and readiness-based placement · math · ages 11–18
Grit is conscientiousness renamed and adds 0.4% to grade prediction; self-control genuinely predicts life outcomes but is 60% heritable with zero shared environment, and training moves ratings, not lives.
mixedconf: highgc: mediumAre self-control and grit teachable levers on achievement? · character · ages 4–18
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
The 10,000-hour rule is dead: practice explains ~14% of performance variance, is itself heritable, and identical twins 20,000 hours apart didn't differ. Necessary, insufficient.
mixedconf: highgc: mediumDeliberate practice and the 10,000-hour rule · deliberate-practice · ages 6–18 · method
Growth-mindset interventions change beliefs almost everywhere and change achievement almost nowhere: the two independent national-scale trials measured standardized tests and found exactly zero.
mixedconf: highgc: lowDoes teaching a growth mindset raise achievement? · character · ages 4–18
Feedback on the task helps modestly; feedback on the person backfires — a stable third of studies reverse. The famous 0.4–0.7 number has no computed source.
mixedconf: highgc: lowFeedback and formative assessment · feedback · ages 5–18 · method
The famous faded-feedback demo doesn't survive meta-analysis; mental practice is real at half the advertised size and never substitutes for physical practice.
mixedconf: highgc: lowFeedback frequency and mental practice in motor learning · motor-skills · ages 4–18
Mastery learning moves tests of what it taught (~0.25) and barely moves independent measures (~0.05) — and time-to-mastery gaps widen, converting ability differences into time.
mixedconf: highgc: lowMastery learning (teach → test → reteach to criterion → advance) · mastery · ages 6–18 · method
The textbook matters at the bottom, not the top: avoid the demonstrated losers; mainstream choices now differ by ~0.02 SD.
mixedconf: highgc: lowMath curriculum choice — how much does the textbook matter? · math · ages 5–14
Varied practice looks worse today and better at retention — in the lab. Applied settings shrink the edge to zero, and it reverses in under-18s.
mixedconf: highgc: lowPractice scheduling for motor skills — varied vs blocked, spaced vs massed · motor-skills · ages 4–18
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
Should a school buy a social and emotional learning programme? · character · ages 4–18
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
Executive function trains like a task, not like a capacity: gains are real, narrow, and gone at follow-up, EF curricula are null under independent trial, and the latent construct is ~100% heritable.
no effectconf: highgc: lowCan executive function be trained, and does it transfer to learning? · character · ages 4–18
Teaching movement teaches movement: the skills improve, but transfer to cognition, achievement, or lifelong activity is near zero in the best trials.
no effectconf: highgc: mediumDoes teaching movement transfer to cognition, achievement, or lifelong activity? · physical-development · ages 4–18
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
No study of homeschooling has a counterfactual — the famous percentile claims are selection all the way down. The honest answer: nobody knows.
insufficientconf: lowgc: highDoes homeschooling raise achievement and attainment, or does it select the children who would have done well anyway? · homeschool · ages 5–18 · structure
Nobody has tested it. There is no controlled trial in which art instruction is the input and independently measured art skill is the outcome — the field's core claim is the one it never studied.
insufficientconf: lowgc: mediumDoes teaching visual art produce artistic skill? · arts · ages 4–18
Homeschoolers get plenty of social contact but measurably fewer, closer peer ties; whether that helps or harms has never been causally tested.
insufficientconf: lowgc: highHomeschool socialisation — the most-asked question, and the least answerable one · homeschool · ages 6–18 · structure
The URL is the state — any view you build here is a permalink you can hand to someone mid-argument.