But an early bedtime may have benefits beyond its direct impact on sleep duration. Indeed, “when a child sleeps is probably as important or maybe more important as how much,” explains pediatrician Marc Weissbluth, author of the best-selling book Healthy Sleep Habits, Happy Child. That’s because the sleep that happens earlier in the night tends to be more restorative than sleep that takes place later at night and in the early morning. So putting your kid to bed early may ensure that a higher proportion of her sleep is the extra-restful kind.

And well-rested kids behave quite differently than sleep-deprived kids. In that same interventional study I mentioned earlier, the 7- to 11-year-olds who were put to bed an hour earlier for five nights were rated by their teachers (who didn’t know that they’d gotten more sleep) as being less irritable and impulsive than usual. A similar study found that four nights of going to sleep an hour earlier made 8- to 12-year-olds more even-keeled and boosted their short-term memory, working memory, and attention skills compared with kids who had their bedtimes shifted later by an hour. Another study found that 2-year-olds who had early bedtimes were, at age 8, 62 percent less likely than those with later or inconsistent bedtimes to have attention problems and 81 percent less likely to have aggression issues. And in a study published last month, Japanese researchers reported that 18-month-olds who went to bed before 10 p.m. were at a lower risk for motor, language, and social deficits compared with kids who went to bed later. One thing to keep in mind, however, is that developmental disorders can also cause irregular sleep patterns, so lack of sleep isn’t always the driver here.