The American Academy of Pediatrics recommends that U.S. secondary schools begin after 8:30 a.m. to better align with the circadian rhythms of adolescents. Yet due to economic and logistic considerations, the vast majority of high schools begin the school day considerably earlier. We leverage a quasi-natural experiment in which five comprehensive high schools in one of the nation’s largest school systems moved start times forty minutes earlier to better coordinate with earlier-start high schools. Here, disruption effects should exacerbate any harmful consequences. We report on the effect of earlier start times on a broad range of outcomes, including mandatory ACT test scores, absenteeism, on-time progress in high school, and college-going. While we fail to find evidence of harmful effects on test scores, we do see a rise in absenteeism and tardiness rates, as well as higher rates of dropping out of high school. These results suggest that the harmful effects of early start times may not be well captured by considering test scores alone.

美国儿科学会建议美国中学从上午8:30开始上课，以更好地适应青少年的昼夜节律。然而，出于经济和物流方面的考虑，绝大多数高中的上学时间都相当早。我们利用准自然实验，在该国最大的学校系统之一中，五所综合性高中将开学时间提前了40分钟，以便更好地与起步较早的高中进行协调。在这里，破坏效应会加剧任何有害后果。我们报告了更早的开始时间对各种结局的影响，包括强制性ACT考试成绩，旷课，高中和学校的准时进度。虽然我们没有找到对考试成绩有害影响的证据，我们确实看到缺勤率和拖延率有所上升，高中辍学率也有所上升。这些结果表明，仅考虑考试成绩可能无法很好地捕捉早期开始时间的有害影响。