If you ever had trouble waking up for an 8:00 a.m. college class, much less taking a test at that time, the results of a new study show you’re definitely not alone. Students' biological clocks — that is, whether they’re a night owl or a morning person — can have a big impact on their grades, depending on the time of day classes are scheduled.

In a study with data from almost 15,000 college students, researchers, from Northeastern Illinois University and the University of California, Berkeley, used the times the participants logged into their school’s computer system to track whether students were “morning larks,” “daytime finches” or “night owls.” Then they looked at how a student's daily rhythms lined up with the grades they got in their classes and the time of day those classes were scheduled.

Social jet lag happens when our body clocks and our daily schedules are out of sync, which is fairly common these days.

They found that only about 40 percent of the students were taking classes at times that worked well with their biological clocks. About 50 percent of the students were enrolled in classes that started too early in the day, and 10 percent were taking classes that started too late in the day for them to be fully alert.

When there was a greater mismatch between a person’s biological clock and their class times, the team found, students tended to get poorer grades. So a night owl taking an early morning class, or a morning lark taking a nighttime class, got lower grades on average.

“We found that the majority of students were being jet-lagged by their class times, which correlated very strongly with decreased academic performance,” said study author, Benjamin Smarr, in a statement. “Because owls are later and classes tend to be earlier, this mismatch hits owls the hardest, but we see larks and finches taking later classes and also suffering from the mismatch.”

This phenomenon, called “social jet lag,” has been studied before in both kids and adults. It happens when our body clocks and our daily schedules are out of sync, which is fairly common these days. Research into its effects on kids has prompted some schools to postpone start times. And it’s not just about grades: Social jet lag has been linked to significant health and mental health issues, like obesity, tobacco use, and excessive alcohol drinking.

The solution may not be so simple as making class times later (although that has been shown to help). The authors suggest a more personalized approach to designing schedules, where the individual needs of the student are determined, and class time structured around that. “Different people really do have biologically diverse timing,” said Smarr, “so there isn't a one-time-fits-all solution for education.”

It may be some time before we see class schedules tailored to students' body clocks, especially since teachers have their own biorhythms to worry about, but it’s certainly an interesting idea, particularly if it boosts learning, attendance and grades. Personalized medicine is becoming more and more a reality, perhaps personalized education is on the horizon?

The study is published in Psychological Science.