Explore the evidence
29 of 88 decisions · clear everything
- math6
- reading6
- early childhood5
- writing4
- assessment3
- health3
- history civics3
- practice3
- science3
- arts2
- character2
- foreign language2
- grouping2
- instruction style2
- motor skills2
- practical2
- time2
- behavior1
- class size1
- computer science1
- curriculum1
- deliberate practice1
- feedback1
- homeschool1
- homework1
- mastery1
- music1
- retention1
- school structure1
- sport1
- talent1
- teachers1
- tutoring1
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
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
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
Yes, on their own terms: lottery-assigned museum and theatre trips move blind-rated analysis of art, plot knowledge and tolerance by 0.08-0.18 SD weeks later, and a film of the same play moves nothing.
moderate supportconf: mediumgc: lowAre museum and theatre trips worth the day out of school? · arts · ages 8–18
Selective CTE high schools raise male graduation 8-10pp and early-career earnings 17-35% on lottery and cutoff designs; test scores, degrees, and every outcome for girls are flat.
moderate supportconf: mediumgc: lowDo career and technical education tracks help students — and which students? · practical · ages 14–18
Immersion costs nothing in English and buys a little — a lottery puts English reading 0.13-0.22 SD ahead by grades 5 and 8 — but no lottery has ever measured how much of the second language students actually learn.
moderate supportconf: mediumgc: lowDoes dual-language immersion work, and is the gain in the second language or in English? · foreign-language · ages 4–18
Teaching handwriting works and transfers: freeing the hand frees composition, with gains still present at six months — even taught in groups of three.
moderate supportconf: mediumgc: mediumDoes handwriting and transcription instruction matter, and should young children type instead? · writing · ages 5–12
Sentence combining improves writing where grammar teaching fails — the same meta-analyses score them +0.50 and −0.32.
moderate supportconf: mediumgc: lowDoes sentence combining improve writing? · writing · ages 5–18
Teaching coding teaches coding: the one clean school RCT gives g=0.47-0.68. Which approach you pick barely matters, and almost every effect size rests on an instrument the developers built.
moderate supportconf: mediumgc: lowDoes teaching programming actually teach programming — and does the method matter? · computer-science · ages 5–18
Formal spelling instruction works (ES 0.54) and more formal beats less formal — explicit wins again, and it transfers beyond spelling itself.
moderate supportconf: mediumgc: lowDoes teaching spelling work, and what does it transfer to? · writing · ages 5–18
Diagnose what a child already knows: teachers cut 40–50% of curriculum for high-ability children and achievement ROSE. The payoff is skipping, not monitoring.
moderate supportconf: mediumgc: mediumPlacement and mastery diagnosis — deciding what to teach next from evidence of current skill · assessment · ages 5–18 · structure
Content-rich history teaching raises history knowledge (g 0.19-0.46) but not standardized reading in under three years; generic 'historical thinking' has no adequately controlled positive result.
moderate supportconf: mediumgc: lowShould history be built on content knowledge or on generic historical-thinking skills? · history-civics · ages 5–18
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
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
The received wisdom that retention is harmful was two measurement errors, not a finding. Fix them and the achievement effect is zero — but the grade at which you hold a child back decides everything.
mixedconf: mediumgc: lowGrade retention — holding a child back versus promoting, and test-based promotion policies · retention · ages 5–18 · structure
Near-zero in primary and almost entirely correlational in secondary. The causal base is three small trials; what the homework IS beats how much of it there is.
mixedconf: mediumgc: mediumHomework — effects by age and by dosage · homework · ages 5–18 · structure
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
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
Taking time away hurts measurably; adding it back buys almost nothing. The return per hour is ~0.02-0.03 SD, concave, and near zero in disorderly classrooms.
mixedconf: mediumgc: lowLength of the school day and year, time-on-task, extended time, and summer · time · ages 4–18 · 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
What parents are asked to DO is the whole effect: tutoring a skill d≈1.15, listening to reading 0.51, reading aloud ~0.18 — same parent, same child. All deflate under better designs.
mixedconf: mediumgc: mediumThe parent as instructor — what survives when the person teaching is the person who raised the child · homeschool · ages 4–18 · method
Trust the composite; distrust the breakdown. Subtest strengths-and-weaknesses replicate at chance on retest, and most of what people read off a score report is noise.
mixedconf: mediumgc: lowWhat a standardized achievement score does and does not license · assessment · ages 5–18 · structure
- Acceleration and gifted programs — the label vs the content
- Algebra timing — acceleration mandates, delay mandates, and readiness-based placement
- Chronic absenteeism — does raising attendance raise achievement?
- Background knowledge and vocabulary as drivers of reading comprehension
- Class-size reduction
- Curriculum choice as a school-level lever
- Deliberate practice and the 10,000-hour rule
- Explicit instruction vs discovery/inquiry — how much guidance?
- Explicit vs reform/constructivist math instruction
- Fadeout — why early gains disappear, and what actually persists
- Feedback and formative assessment
- Ability grouping and tracking — four practices, four verdicts
- The early home environment — what parents can and cannot causally move
- Interleaving (mixing problem types vs blocking)
- Manipulatives and concrete-representational-abstract (CRA) sequences
- Mastery learning (teach → test → reteach to criterion → advance)
- Math curriculum choice — how much does the textbook matter?
- Math-fact fluency and timed practice (and the anti-timed-test claims)
- Feedback frequency and mental practice in motor learning
- Practice scheduling for motor skills — varied vs blocked, spaced vs massed
- Breakfast, school meals, and micronutrients — what feeding children actually buys
- Phonemic awareness training (and whether it needs letters)
- Systematic/explicit phonics vs whole language and balanced literacy
- Preschool at scale — Head Start, state pre-K, and what universal provision delivers
- Perry Preschool and Abecedarian — what the famous studies actually establish
- Reading-comprehension strategy instruction (reciprocal teaching, summarizing, questioning)
- Reading fluency — guided repeated oral reading, and whether repetition matters
- Reading Recovery and Tier-2 1:1 early-literacy tutoring
- Retrieval practice (the testing effect)
- School spending, charters, and what school-level choices actually move outcomes
- School starting age, relative age, and academic redshirting
- Spaced (distributed) practice
- Talent and trainability — what is heritable, and what that does not license
- Teacher quality — selection over credentials and workshops
- Tutoring — the honest effect, the Bloom 2-sigma myth, and what survives scale
- Vision — outdoor time against myopia, and screening and correction for achievement
- Word problems, schema instruction, and the conceptual-vs-procedural question
- Worked examples (studying solutions vs solving problems)
- Early sport specialization, talent selection, and the relative age effect
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