Start Time and Benefits of 30 minutes of delay
Research has demonstrated that any change that increases the amount of sleep students get is a move in the right direction.  While ideally all students would get sufficient sleep, and while a 30 minute change is unlikely to produce that result, research has found that it will be beneficial.

Owens, J. A., Belon, K., and Moss, P. “Impact of Delaying School Start Time on Adolescent Sleep, Mood, and Behavior.” Archives of Pediatric & Adolescent Medicine, 164.7: pp. 608-614. 2010. p. 612.


Findings from that study:  

summarized by: Michael J Breus, Is it Time to Start School Later, Psychology Today

Researchers collected data about sleep habits during a winter term when school start time was delayed from 8 a.m. to 8:25 a.m. They found this modest adjustment to the beginning of the school day was associated with significant changes to sleep and waking mood:

  • Students’ overall sleep duration increased significantly when their school day began 25 minutes later. Total sleep time increased by an average of 29 minutes.

  • With the later start to the school day, the percentage of students sleeping 8 or more hours per night more than doubled, from 18% to 44%.

  • Younger students (grades 9 and 10), as well as students who were sleeping less at the study’s outset showed the greatest benefit from the 25-minute adjustment to school start time.

  • Students also experienced significant reduction in daytime sleepiness, as well as improvements to mood, during the later school-start period.

  • Caffeine use among students also reduced during this period.

  • Students’ daytime activities—time spent doing homework, and time engaged in extracurricular activities including sports—did not change with the alteration in the start to the school day.

  • When the students’ school start time returned to 8 a.m. after the end of the winter term study period, students lost the sleep gains they had achieved. Their sleep duration returned to levels that researchers observed at the study’s outset. 

http://thechart.blogs.cnn.com/2010/07/05/small-delay-in-school-start-timesbig-benefits/

In the current study, researchers looked at just over 200 students in grades nine-12 at a private school. The students took a survey, both before and after the school start time was changed from 8 a.m. to 8:30 a.m. to find out about sleep-related problems and both sleep and wake behaviors.

Overall, the number of students who reported feeling unhappy, depressed, annoyed or irritated decreased. Also, fewer found themselves at the health center for fatigue-related concerns.

"If you really need nine hours, and you're only getting six and a half hours or seven hours, even that extra half-hour can make a big difference," Owens said. She says future studies should include looking at academic performance.

http://archive.boston.com/news/nation/articles/2010/07/06/study_shows_teens_benefit_from_later_school_day/

Giving teens 30 extra minutes to start their school day leads to more alertness in class, better moods, less tardiness, and healthier breakfasts, a small study found.

“The results were stunning. There’s no other word to use,’’ said Patricia Moss, academic dean at the Rhode Island boarding school where the study was done. “ We didn’t think we’d get that much bang for the buck .’’ 

Winsler A. et al, Sleepless in Fairfax: The difference one more hour of sleep can make for teen hopelessness, suicidal ideation and substance use, Journal of Youth and Adolescence, 2015 Feb; 44(2)


Findings: benefits accumulate across the hours:

"Supporting our hypotheses, we found that reduced sleep was strongly associated with each of the adverse health outcomes we examined among Fairfax County youth. Controlling for background variables, the odds of a student feeling sad and hopeless increased by 38 %; of reporting serious suicidal ideation, by 42 %, and of having already attempted suicide increased by a striking 58 % for each hour less of sleep a student obtained. These odds accumulate multiplicatively with each hour of sleep lost such that for a student receiving three less hours of sleep (e.g., 5 h/night - compared to a student receiving 8 h) the beta coefficient would be multiplied by 3, yielding odds ratios of 2.64, 2.85, and 3.92 respectively, making such a youth more than 2.5 to almost 4 times more likely to be depressed and/or suicidal."

and between sequential hours

"Importantly, our study shows the difference a mere hour of sleep can make in terms of increasing the odds of adverse outcomes in adolescents. Many of the prior studies categorize students into either a reduced sleep group (defined variously as 6 or 7 or 8 h/night) or a normal sleep group, showing that those who obtained considerably less sleep are more likely to have negative outcomes than those who garner sufficient sleep (McKnight-Eily et al. 2011; Mednick et al. 2010). Our findings suggest, however, that even within what are often considered normal sleep ranges of 7 versus 8 h, just 1 h less of adolescent sleep is associated with statistically and practically significant increases in the probability of experiencing multiple adverse health outcomes. The difference between 6 versus 7 h of sleep is similarly striking. Experimental studies have also revealed important health and performance benefits in youth who obtain only 45–60 min more of sleep (Dexter et al. 2003; Owens et al. 2010)."

"The present study found that the odds of teen hopelessness, suicidal ideation and suicide attempts, and substance use are sizeably reduced with one more hour of weeknight sleep. Thus, it appears that one does not have to make a huge leap from obtaining, say, 6 h to getting nine hours of sleep as a teen in order to see the positive health benefits of increased sleep. Attention to, and intervention for, reduced adolescent sleep is critically needed at multiple levels (individual, family, school, and community) in order to optimize the mental health and well-being of adolescents."
Continuous Benefits Graph

A 2020 Vision for Public Education in Ulster County: Later School Start Times for Adolescents, The Center for Research, Regional Education and Outreach, SUNY New Paltz Ulster County School Boards Association, August 2014


Several case studies, including:
Already in New York State, Glens Falls switched its high school start time from 7:45am to 8:26am, and is reporting positive results; assistant high school principal Elisabeth Collins reported that data show, “our students are getting up to 30 minutes more of sleep a night, our discipline write-ups have lessened, our tardiness rate is not as severe as it was 2 years ago. And another very important point is that the students are failing fewer courses in their day” 

Hanover Research, Impact of School Start Time on Student Learning, February 2013

"Researchers have shown that even a modest delay in school start time (30 minutes) produces improvements in measures of student mood, alertness, and health in adolescent students."