This may have serious physical, mental, and social consequences for adolescents and negatively impact their academic performance. There is mounting medical evidence that amount of sleep, time of day, and circadian rhythms, i.e., rhythmic cycles of the body, do play a part in how prepared an adolescent is to learn. Studies have shown, for example, that sleep deprivation is associated with memory deficits, impaired performance and alertness, and delayed responses. Students experiencing sleep deprivation can also experience an increased potential for drug and alcohol use, as well as vulnerability for accidents. Not only is the proper amount of sleep important for cognitive processes to function adequately, but the time of day also has an effect on learning.
Research indicates that many high school students do their best learning in the afternoon.
One study found that afternoon reading instruction produced the greatest increase in reading scores as compared to morning instruction. However, most exams, such as the SATs and ACTs, are administered during morning hours. According to researchers, adolescents experience a natural circadian phase delay and therefore, stay up later and sleep in later than in preadolescence. It is not uncommon for many teenagers to sleep until the mid-afternoon during the weekends. Despite the increasing need for sleep, many adolescents are actually getting less and less.