Explore the evidence
24 of 88 decisions · clear everything
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
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 measured effects reverse. The famous 0.4–0.7 number has no computed source.
mixedconf: highgc: lowFeedback and formative assessment · feedback · ages 5–18 · method
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
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
Should a school buy a social and emotional learning programme? · character · ages 4–18
Capitalisation and punctuation move when directly taught and directly measured, and don't move when embedded in writing programmes. A teachable subject, not a writing lever.
mixedconf: mediumgc: mediumCan capitalisation, punctuation and usage be taught directly as their own subject? · writing · ages 5–18
Explicit form-focused teaching beats pure exposure, so the archive's negative verdict on L1 grammar does NOT transfer — but the effects are measured on the taught forms, immediately, mostly on adults.
mixedconf: mediumgc: lowComprehensible input or explicit grammar teaching — which builds a second language? · foreign-language · ages 4–18
Life-skills courses reliably teach the content and rarely change the conduct; behaviour moves only where instruction sits close in time to the decision, and driver education is worse than nothing.
mixedconf: mediumgc: lowDo life-skills courses — money, cooking, driving, health — change what students actually do? · practical · ages 6–18
Civics teaching buys civic knowledge (d = 0.49) that fades to the control mean in two years and moves neither attitudes nor validated turnout; what moves voting is school quality and noncognitive skill.
mixedconf: mediumgc: lowDoes civic education produce civic knowledge, and does civic knowledge produce civic behaviour? · history-civics · ages 5–18
The headline effects are a measurement artefact: drama gives d≈0.89 on researcher-made tests and d≈0.29 on standardized ones, and the two randomised trials with standardized outcomes are null.
mixedconf: mediumgc: mediumDoes classroom drama build verbal and literacy skills? · arts · ages 5–16
Document-based instruction reliably improves the sourcing and argument tasks it teaches (g ≈ 0.42) and, in the two best-identified trials, moves neither standardized reading nor history knowledge.
mixedconf: mediumgc: lowDoes document-based source work move history knowledge, reading comprehension, or neither? · history-civics · ages 8–18
Sort by what the software replaces: adaptive drill inside the school day buys +0.05-0.20 SD; a device, a connection or the teacher buys zero to negative; LLM tutors have no usable evidence at all.
mixedconf: mediumgc: lowDoes educational technology raise learning — CAI, adaptive software, devices, screens, and AI tutors? · edtech · ages 5–18 · structure
Not at school: the largest randomised trials find nothing on reading, maths or cognition. A small effect on laboratory executive-function tasks is contested, may be real at ~0.2 SD, and is end-of-treatment only.
mixedconf: mediumgc: mediumDoes learning music make children smarter or better at school? · music · ages 4–16
Classroom order is causally worth a great deal — one disruptive peer costs classmates 3% of adult earnings — yet no branded behaviour programme reliably delivers it and exclusion makes things worse.
mixedconf: mediumgc: lowHow should a school run its classrooms and its discipline system? · behavior · ages 4–18 · structure
Guided inquiry is positive in 16 of 16 PISA regions and unguided inquiry negative in 18 of 20 — but the programmes built on that finding go to zero at scale: +0.22, then +0.01, then +0.02 on the same test.
mixedconf: mediumgc: lowInquiry-based science teaching vs explicit and textbook science teaching · science · ages 8–18
Attainment falls steadily with age of first exposure, but the sharp critical period is contested and an earlier classroom start buys nothing durable: start young for immersion, not for two lessons a week.
mixedconf: mediumgc: mediumIs there a critical period for learning a second language, and when should a child start? · foreign-language · ages 4–18
One systematic review kept 39 studies from 11,771 records; another found 1 RCT among 53. What evidence exists favours interest (+0.12) over attainment (+0.01), and simulations match real apparatus.
mixedconf: mediumgc: lowLaboratory and practical work in school science · science · ages 5–18
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: lowPerry Preschool and Abecedarian — what the famous studies actually establish · early-childhood · ages 4–5 · structure
Conceptual-change teaching reliably moves the test and nothing shows it removes the intuition. Corrected for design and publication bias, a taught unit is g≈0.64 and a refutation text g≈0.28.
mixedconf: mediumgc: lowScience misconceptions and conceptual change — can naive intuitions be taught away? · science · ages 6–18
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: mediumTest preparation — does coaching raise scores, and does a raised score mean raised ability? · assessment · ages 5–18 · structure
The URL is the state — any view you build here is a permalink you can hand to someone mid-argument.