A new research study out of the University of California, Los Angeles, reports the "somewhat surprising" finding that spending extra time studying tends to negatively affect high school students' academic performance in school the next day. But there's also a perfectly logical explanation for this: When students study more, the researchers found, they tend to sleep less.

For the study, the researchers monitored students at three Los Angeles high schools for 14-day periods three years in a row. They asked the students to complete daily checklists to keep tabs on the amount of time they spent studying each day, how many hours they slept, and their daily academic experiences.

The study, published in Child Development, reports that "days on which students reported longer than normal study times tended to be followed by days with more academic problems." By the same token, "days on which students reported longer than normal study hours tended to be days on which they reported fewer hours sleep." Both associations grew stronger as the students progressed through high school.

The findings, according to the researchers, suggest not that studying more is necessarily problematic (sorry, kids) but that "it is particularly counterproductive to sacrifice sleep in the service of study." In this respect, the study corroborates previous research showing that that students who sleep more hours on average tend to have better academic outcomes.

In light of the findings, the study notes, studentsand, by association, educatorsmay need to consider the sleep-study trade-off more carefully. As possible solutions, the researchers recommend that students try to maintain more consistent daily study schedules, use in-school study periods more productively, andif necessarycut down on other activities. (There's that one-to-two hours of daily T.V.-watching, for example.)

In general, the study notes, adolescents need more than nine hours of sleep nightly, but only 9 percent of high school students get that.

