Generated view: 15 sources whose Kunskapsbank note was filed under this theme, and the claims and candidates they link to.
C14 weakened
Starting the secondary-school day later has let teenagers sleep longer and improved their school results in several studies, but not consistently: when one New York high school started 45 minutes later, students at first reported about 20 minutes more sleep, the gain was gone a year later, grades did not change in the two years after the change, and state exam scores showed no consistent change in the first year after (the only year compared) (Thacher & Onyper 2016).
Serves: Q1
Ages: grundskola-hog, gymnasium
Bounds: Secondary-school (roughly ages 11-18) start times, outcomes measured sleep and grades or test scores; not evening screen use (candidate K04) or sleep hygiene programmes. Evidence on file: Dunster et al. 2018 (Science Advances; Seattle start delayed nearly an hour; median sleep +34 min, median grades +4.5%, attendance improved; pre/post, not randomised); Edwards 2012 (Economics of Education Review; Wake County, North Carolina middle schools; later starts associated with higher test scores, larger for lower-scoring students). Related lab evidence: Cousins et al. 2019 (sleep restriction impaired adolescents' long-term retention). Consistency bound (added 2026-10-17, nightly attack; enriched 2026-11-06): Thacher & Onyper 2016 (Sleep 39(2), 271–281; full text read): one public high school in Glens Falls, New York, moved first period from 07:45 to 08:30; self-reported sleep rose by about 20 minutes two months after the change and was back to baseline a year later; the share reporting ≥8 h sleep went 40% → 60% → 50% (a net ~10 pp lasting gain in the upper tail while mean TST rebounded); tardiness fell (unexcused tardy ratio 0.066 → 0.05) and disciplinary incidents fell and stayed lower; absences rose in the within-student analysis (all-absence ratio 0.085 → 0.113, about +5 days/year; same-student subset 12.8 → 17.7 days/year) — a cross-sectional roster count without repeated measures wrongly suggested a tiny decrease; course-failure rate among students who experienced the change spiked to 6.04% in the transition year then returned (4.72%, 4.49%, 6.04%, 4.39%; χ²(3) = 14.31, P = .003); no change in grades in cohort-sequential analyses of 2010–2014 records (two years before and two after), and no consistent change in Regents exam scores when 2011–2012 was compared with 2012–2013 (the only year after the change that was compared). One school, no comparison school, self-reported sleep. Kill-condition test survived 2026-10-16 (James et al. 2023, grades prong). Kill-condition test survived 2026-10-22 (Dou, Gihleb, Giuntella & Lonsky 2026, NBER Working Paper 35184, DOI 10.3386/w35184; working paper, not peer reviewed); figures corrected 2026-11-12 to the October 2026 revision of the paper: after California's statewide mandate (SB 328; middle schools no earlier than 8:00, high schools no earlier than 8:30), the share of high-school students reporting at least 8 hours' sleep rose 3.6 percentage points (13%) against other states, and teenagers' (ages 15–18) weekday diary sleep about 28 minutes (0.46 hours). Test scores now come only from a within-California comparison: schools in counties where the mandate forced a bigger shift (earlier pre-policy starts, proxied by teachers' commute arrival times) against schools in counties that already started late or were rural; the share of students meeting state standards rose about 1.7–1.8 percentage points in maths, English and science in high school and about 1.7 in grade-8 maths and English (0.7 in science, p < .10), growing over 2023–2025. The revision drops the earlier cross-state comparison of grade-8 scores (about 0.10 and 0.08 standard deviations against matched districts in other states in the May 2026 version), because, in the authors' words, cross-state comparisons of test scores after 2022 cannot isolate the policy; the within-state design does not rule out counties recovering from the pandemic at different speeds. Sleep self-reported, scores and sleep from different data sets; the kill still fails on the revised paper (more sleep, higher test scores), but on weaker identification. Review context: Marx et al. 2017 (Cochrane Database of Systematic Reviews, CD009467; abstract and plain-language summary only): 11 studies, evidence rated very low quality; six studies found more sleep with later starts; four studies of academic outcomes gave mixed results.
Attack record: 3 attacks: 2 survived, 1 narrowed · Evidence links: 9 linked sources (7 supports, 2 limits)
9 link(s) from sources in this view.
C21 weakened
Getting enough sleep in the nights before learning protects what was learned: several nights of short sleep before encoding cause more forgetting of factual material weeks later than adequate sleep. Short sleep after learning also tends to lower later memory: across studies, restricting sleep after encoding impairs memory about as much as restricting it before (Crowley et al. 2024; mostly single nights; how long after learning memory was tested was not analysed), although the one multi-night study of factual prose retained over weeks found no clear increase in forgetting (Lo, Bennion & Chee 2016).
Serves: Q1 (How do humans actually learn, and what helps them learn best?)
Ages: gymnasium, vuxen-livslangt
Bounds: Multi-night sleep opportunity before encoding of factual material, with retention measured days to weeks later; not school start-time policy itself (C14) and not retrieval practice (C0). Kill-condition test survived 2026-10-27 (Cousins, Wong & Chee 2019, Journal of Adolescent Health 65, 549–557, DOI 10.1016/j.jadohealth.2019.04.030; OA full text stored from lab mirror): adolescents 15–18, 5 nights × 5 h time-in-bed vs 9 h; learning after the fourth restricted night; more forgetting after short sleep (+26% at 30 min, d = .66; +34% at day 3, d = .69; +65% at day 42, d = 1.17); vigilance worse but not significantly correlated with the memory outcome. Weakened 2026-10-27 (Lo, Bennion & Chee 2016, Journal of Sleep Research 25, 664–672, DOI 10.1111/jsr.12424; OA full text stored): after encoding a prose passage, 7 nights × 5 h vs 9 h TIB; no main effect of group on free recall (F(1,43) = 1.13, P = .29); authors report no significant memory differences at any time point (initial, 1 week, 6 weeks) between SR and control for highlighted, non-highlighted, or total content; only the growth of the prioritization benefit from immediate to 1 week was significant in control (d = 0.99) not SR (d = 0.26). Diekelmann & Born 2010 (Nature Reviews Neuroscience 11, DOI 10.1038/nrn2762; abstract): sleep optimises consolidation (review; full text not yet read). Voderholzer et al. 2011 (Sleep Medicine 12, DOI 10.1016/j.sleep.2010.07.017; closed from the box; cited by Lo 2016 and Cousins 2019 as a post-learning consolidation null) remains a future lead, not applied. Spacing bound and further support (corrected 2026-10-28): Huang, Deshpande, Yeo, Lo, Chee & Gooley 2016 (SLEEP 39(9), 1681–1690, DOI 10.5665/sleep.6092; PMC full text): Singapore boarding-school adolescents 15–19 randomised to 5 h or 9 h time in bed for 7 nights while learning 40 GRE-type word pairs; words crammed in one session were recalled worse after short sleep (Tukey P < .001), but words spaced over four days were recalled as well (P = .80; spacing × sleep LR χ² = 8.40, P < .01), and the gap on crammed words remained after one review pass (P < .01; spaced P = .99). In an exploratory split by study day, crammed words learned after the last normal night were recalled as well (P > .99) while those learned after restricted nights were worse (P < .01, P < .001) — consistent with both halves of the claim. Limits: restriction came both before and after each study day, so it is not a clean pre-encoding-only test; the set split was exploratory; the authors say the spaced items may have been over-studied (ceiling) and no power analysis was done. See open question 17. Weakened again 2026-11-01 (Crowley, Alderman, Javadi & Tamminen 2024, Neuroscience & Biobehavioral Reviews 167, 105929, DOI 10.1016/j.neubiorev.2024.105929; CC BY full text, Kent repository): 125 effect sizes from 39 reports (N = 1,234), 3–6.5 h vs 7–11 h for 1–14 nights; overall g = 0.29 (CI 0.13 to 0.44); restriction after encoding g = 0.36 (CI 0.16 to 0.56; k = 72; 0.25 without outliers) vs before encoding g = 0.24 (CI 0.02 to 0.46; k = 43; 0.21 without outliers); timing not a significant moderator (p = .40); number of restriction nights not a moderator (p = .57); Lo et al. 2016's own post-encoding outcomes coded in the direction of impairment (g = 0.09 to 0.41, not significant in that study). The claim's 'after learning does not clearly increase forgetting' is withdrawn as a general statement; it is kept only as the result of the one multi-night factual-prose study. Limits of the meta: 60% single nights, only one effect size beyond 7 nights, nearly all non-declarative outcomes post-encoding, mostly single nights; the retention interval was not coded or analysed (Crowley §2.4, §2.7.5). In the combined restriction plus total-deprivation analysis, restriction before encoding gave g = 0.20 (CI 0.01–0.39) against 0.63 for total deprivation (§3.5); mean post hoc power 15.41% (range 7.61–25.19%); Egger asymmetry z = 3.90 with no bias in the selection model; not preregistered (§2.1, §3.2, §4.3). The first sentence's "weeks later" still rests on Cousins et al. 2019.
Attack record: 3 attacks: 1 survived, 2 narrowed · Evidence links: 7 linked sources (3 supports, 4 limits)
4 link(s) from sources in this view.