There has been much recent interest in the proposed relationship between school start times and adolescent sleepiness. Although adolescents tend to have a sleep 'phase-delay', such that they tend toward later bedtimes and rising times, school start times become earlier and earlier as students progress from elementary, to junior high, to high school. Preliminary cross-sectional studies suggest that high school students attending schools with an earlier start time tend to get less sleep than those attending high schools with a later start time (Allen, 1991), and that total sleep tends to decrease as students transition from junior high to an earlier-starting high school (Carskadon, Wolfson, Acebo, Tzischinsky, & Seifer, 1998).

The Minneapolis public school system instituted a change in school start times beginning with the 1997-1998 school year. High school start times were moved from 7:15 to 8:40 a.m. and middle school start times were shifted from 7:40 to 9:40. Individual elementary school start times were set at 7:40, 8:40, or 9:40. Kubow, Wahlstrom, and Bemis (1999) have reported the preliminary results of teacher surveys and teacher and student focus groups regarding the perceived effects of the change in school start time. The reactions were mixed. More than half (57%) of the high school teachers reported that students were more alert during morning classes than they had been with the earlier start time. There were concerns among urban students and their teachers, however, that the new schedule interfered with students' available time for homework and studying as well as with their work hours and income, social opportunities, and extracurricular activities. Teachers also noted safety considerations associated with the later school end-time. Interestingly, suburban high school students and teachers tended to have a more positive take on the later school start time. The study authors propose that the later school start-time may influence different school populations in different ways, due to disparities in the availability of private transportation and/or other factors. Although not at all definitive, these findings suggest that changing school start-times in response to concerns about adolescent sleepiness is likely to have both positive and negative consequences.