A new paper published in Scientific Reports adds more meat to the argument that school should start later in the day: researchers found that school schedules affect night owls’ grades, but interestingly, only in specific subjects, as The British Psychological Society digest reports.

Giulia Zerbini of The University of Groningen and her colleagues looked at more than 40,000 individual exam scores—across different school subjects—from 523 Dutch students between 11 and 17-years-old. Students also completed something called the Munich ChronoType Questionnaire, which assessed their chronotype, categorizing them as either larks (those who wake up and go to bed early) or owls (those who stay up and get up later). 

Additionally, the researchers accounted for “social jetlag,” the difference between your natural rhythms and the schedule that your life demands you keep. For instance, a night owl with an early class would probably experience social jetlag because it would be hard for them to fit in a good night’s sleep on that schedule, BPS writer Helge Hanselmann explainedStudents also reported any differences in sleep habits on weekends versus the school week.

The researchers found that not only did owls get lower grades compared to larks, but the negative association between being an owl and doing poorly in school was “similar to the association between absenteeism from school and poorer grades,” Hanselmann wrote

Surprisingly, even when owls slept enough (according to the National Sleep Foundation kids between 6-13-years-old should get 10-13 hours of sleep, and teens 14-17-years-old should aim for 8-10 hours of sleep), they still performed worse on exams compared to larks. Hanselmann wrote that this might be because owls have difficulty “performing at their best during certain school hours.” This theory seems likely because when the owls took the same exam later in the day, they got similar grades to larks. Being an owl was also linked to having “an increased risk of dismissal from class, late arrival and social jetlag,” Hanselmann wrote.

It gets even more interesting though: owls did worse on specific subjects. They performed worse in areas like science (not including physics), but fared just as well as larks in humanities or linguistic subjects. Hanselmann explains that this might be due to the fact that, as previous studies have found, “chronotype and time-of-day variation in performance have the most pronounced effects in areas demanding fluid intelligence, such as mathematics.”

Hopefully, these findings add urgency to changing early school start times—something senior behavioral and social scientist at the RAND Corporation Wendy Troxel, PhD, called a threat to public health. The body of research is large enough now that we’d be wise to stop ignoring it. 

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