It is by now well known that human beings are biologically programmed to have shifts in their circadian rhythms during the teen years, resulting in teenagers being most alert during the evenings.  Yet we persist in forcing them to conform to a more adult daily pattern.  Suggestions to start school classes later in the day for that age group have often been ignored, even though the scientific evidence is clear that it would result in improved learning by better accommodating their natural biological patterns.  A study published last week in the Journal of Clinical Sleep Medicine that can be found here (subscription required) now shows that teenaged drivers have higher accident rates earlier in the morning, also attributed to forcing them to adopt a daily pattern that is biologically unnatural.  It is worth highlighting this research yet again:  sleep deprivation in teens has been linked not only to moodiness, irritability, and learning disadvantages but also to behavioral problems that are a consequence of attempting to deal with the deprivation, notably the excessive use of stimulants to stay awake during the day and the use of alcohol to fall asleep at night.  Moving school start times later in at least Minnesota, Massachusetts, and Kentucky have resulted in identifiable improvements in student punctuality and efficiency as well as a reduction in behavioral problems.