Matthew Walker on education: what the evidence says · JRE #1109
SUBJECT: EDUCATION
The short answer
Walker claims that Edina, Minnesota shifted its high school start time from 7:25 to 8:30 a.m., and that in the year before the change the top 10% of students averaged an SAT score of 1288. The Edina, Minnesota start-time shift and the SAT figures Walker cites derive from real school-district data collected as part of research led by Kyla Wahlstrom at the University of Minnesota in the 1990s, and this anecdote has circulated widely in popular sleep-science writing, including Walker's own book.
Not a true/false call. Every claim is logged with its sources; read the exhibits below.
They shifted school start times from I think it was at 7:25 to 8:30 in the morning and they look at SAT scores and in the year before they made the time change the top 10% performing students got an average SAT score of 1288.
What the evidence says 01 / RECORD
The Edina, Minnesota start-time shift and the SAT figures Walker cites derive from real school-district data collected as part of research led by Kyla Wahlstrom at the University of Minnesota in the 1990s, and this anecdote has circulated widely in popular sleep-science writing, including Walker's own book. However, that single-district, pre-post comparison cannot isolate start time as the cause of the SAT change, since the shift coincided with other confounding factors, including a nationwide recentering of SAT scoring in 1995-96 and normal year-to-year cohort variation, and it was not a controlled study. A 2022 systematic review in Sleep Medicine Reviews examined 21 studies on school start times and academic achievement (grades and test scores) and found no generalizable improvement in achievement associated with later start times: results across studies were mixed, with roughly as many showing no association as showing positive, negative, or unclear effects, and most studies carried substantial risk of bias. Separately, later start times are well supported by other research as increasing adolescent sleep duration and improving certain mental health and behavioral outcomes, an association documented in Wahlstrom's own later multi-district survey work, but that same body of research does not establish start time as a reliable driver of higher test scores. Overall, the specific SAT anecdote is a real but cherry-picked and confounded data point, while the broader causal claim that delaying school start times raises standardized test scores is not well supported by the current peer-reviewed literature.