Researchers from The University of McGill say delaying school start times could help Canadian teenagers sleep better—giving them a better chance for success.

In a study published in the Journal of Sleep Research, the researchers found that students from schools that started earlier slept less and were more often tired in the morning. The findings help explain why, according to recent data, one in three Canadian teenagers don’t get enough sleep.

“The problem is that early school start times conflict with the natural circadian clock of teenagers,” says lead author of the study Geneviève Gariépy. “As teenagers go through puberty, their circadian clock gets delayed by two to three hours. By the time they reach junior high, falling asleep before 11 p.m. becomes biologically difficult, and waking up before 8 a.m. is a struggle. Adolescents are fighting biology to get to school on time.”