Here’s a surprise. Naps may not be good for your children! According to the London Daily Mail, new research found that kids who doze during the day get less sleep at night, falling asleep an average of 40 minutes later than non-napping kids. Nappers also had a harder time getting up in the morning, were more moody, and more likely to resist going to school. Even more surprising: Those behaviors lasted even after the children stopped taking naps. Perhaps because of the lasting influence of napping on their sleep and wake cycles.

Dr. Joe McNamara of the University of Florida thinks napping may also affect mental performance. He measured how well kindergarten children could solve puzzles that measure planning and organizational skills. The result: The kids who took longer naps completed fewer puzzles successfully. The later they went to bed at night, the worse they performed. In fact, even though all kids – nappers and non-nappers – got the same total amount of sleep, kids who skipped the naps and did all their sleeping at night were more cheerful and more focused during the day.