Explore the evidence
15 of 88 decisions · clear everything
- math6
- reading6
- writing6
- early childhood5
- science5
- arts4
- character4
- health4
- assessment3
- debunked3
- foreign language3
- history civics3
- homeschool3
- practice3
- grouping2
- instruction style2
- motor skills2
- music2
- practical2
- time2
- transfer2
- behavior1
- class size1
- computer science1
- curriculum1
- deliberate practice1
- edtech1
- feedback1
- homework1
- mastery1
- physical development1
- retention1
- school structure1
- sport1
- talent1
- teachers1
- tutoring1
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
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
Comprehension is knowledge — but vocabulary teaching moves standardized comprehension only d≈0.10. The big content-knowledge bet (Core Knowledge lottery, 0.24) is real and unreplicated.
moderate supportconf: mediumgc: lowBackground knowledge and vocabulary as drivers of reading comprehension · reading · ages 5–14
Mixing problem types helps where confusion is the enemy — discriminating similar categories, mixed math practice — and is useless or worse for facts and prose.
moderate supportconf: mediumgc: lowInterleaving (mixing problem types vs blocking) · practice · ages 10–18 · method
Phonemic awareness transfers to reading only with letters attached: speech-only training peaks near 10 hours and moves reading d=0.19; with print, 0.66.
moderate supportconf: mediumgc: lowPhonemic awareness training (and whether it needs letters) · reading · ages 4–7
Guided oral reading works, but the ingredient is volume, not repetition: at equal exposure, re-reading has no edge over wide reading.
moderate supportconf: mediumgc: lowReading fluency — guided repeated oral reading, and whether repetition matters · reading · ages 6–12
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
Two reviews screened ~12,000 records and found one RCT and six quasi-experiments. 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
Reading Recovery buys large short-term gains at high cost; the only US long-term estimate is negative. Early 1:1 tutoring works — this model's durability is unproven.
mixedconf: mediumgc: lowReading Recovery and Tier-2 1:1 early-literacy tutoring · reading · ages 5–8
Strategy instruction is a one-time boost, not a trainable skill: six sessions buy what fifty do, and modern at-scale trials are ~null.
mixedconf: mediumgc: lowReading-comprehension strategy instruction (reciprocal teaching, summarizing, questioning) · reading · ages 8–14
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
Narrow reasoning routines are teachable and stay taught for seven months. The far-transfer claim failed its one randomised test: science −0.01, English −0.15, maths −0.11.
no effectconf: mediumgc: lowTeaching students to think scientifically — does it transfer? · science · ages 7–18
No trial has ever varied the sequence of science content and measured the result. The one quasi-experimental test of course order found nothing, and depth-over-breadth is a retrospective survey worth 0.08-0.13 SD.
insufficientconf: mediumgc: mediumScience content sequencing — coherence, prerequisites, and course order · science · ages 5–18
The URL is the state — any view you build here is a permalink you can hand to someone mid-argument.