In a previous post I discussed some of the benefits of having later school start times for junior high and high school students. Studies conducted in both public and private school systems in the USA have shown that even one more hour of sleep per night results in improved mood, attention and learning for students. Research is beginning to explain why sleep is so important for effective learning. Two studies, including one conducted outside the USA, support and extend earlier findings.
The first study, carried out by Lufi, Tzischinsky & Hadar in a public school in Israel, showed that delaying the school start time resulted in students sleeping about 55 minutes longer per night than a control group kept on the usual early schedule. This is an important finding in its own right as it confirms what earlier studies have indicated - when school starts later students actually use the time for sleeping and are not spending another hour on the computer, watching TV, socializing or doing home work. Two classes of students were assigned randomly to either the experimental group with an 8:30 AM start time or the control group with the standard 7:30 AM start time. Both boys and girls participated and the average age was 13.78 years. A significant aspect of the study was the cooperation of the transportation system and parents in accommodating the new schedule for the experimental group. The students in the experimental group showed significantly better performance on tests of attention and concentration. The tests used indicated that the students in the experimental group had better attention, were less impulsive and performed better. It was not clear whether the improvement was due to sleeping more or just being able to sleep later. This study strongly suggests that making a single change, a one hour later start time, could significantly improve cognitive functioning among middle school students.
A second study, by Vorona and colleagues, compared two cities in Virginia with different school start times on motor vehicle accident rates between their respective students. The two communities involved were near to each other and had similar demographic profiles. The interesting difference is that one of the school systems starts 75 to 80 minutes earlier than the other. DMV records were reviewed for drivers between 16 and 18 years of age for 2007 and 2008. The motor vehicle accident rates for the community with the earlier start time were 65.8/1000 in 2008 and 71.2/1000 in 2007 while the community with later start times had teen crash rates of 46.6/1000 in 2008 and 55.6/1000 in 2007. Differing degrees of traffic congestion were considered and did not account for the difference in crash rates.
There are several possible explanations for these findings. They include the possibility that less sleep for the students with an earlier start time results in poorer cognitive functioning due to problems such as slower reaction time. Cognitive difficulties may be caused by students having to be awake during the portion of the circadian rhythm during which they would naturally prefer to be asleep. It is also possible that "sleep inertia" has an effect. Sleep inertia is a period of an hour or more of poor cognitive functioning that occurs after waking and before being fully alert. For the students having to leave home soon after getting up from bed in order to get to school on time, this could result in poor judgment and poor reaction time placing them at greater risk for accidents. This study supports the recommendation for a later school starting time as it relates to the physical safety of our young people and other drivers.