Ask any parent and they'll agree: when kids don't get enough sleep, they're cranky with a capital "C" the next day. That's kind of a no-brainer. But a study from 2013 claims that when kids get random amounts of sleep — early bedtime one night followed by a late night the next — they can be just as cranky, if not more so.

For the study, researchers looked at the sleep patterns of over 10,000 British school children at ages 3, 5 and 7. Parents were asked about the regularity of kids' bedtimes, particularly during the school week as well as information about their children's conduct problems, hyperactivity, emotional symptoms, or ability to get along with peers. Teachers were also given the opportunity to weigh in on each child's behavior once they were in school.

It came as no surprise that kids with a late bedtime — after 9 p.m. — had more behavior issues than their early-to-bed peers. But what was surprising was that kids with random bedtimes had more behavior problems than the kids who regularly got a shorter night's sleep. You can read all of the details of the study in this post: Want well-behaved children: Put them to bed on time.

These results fall right in line with the study I wrote about this summer that found kids with irregular bedtimes had lower test scores in school.

Change in sleep patterns tied to academic performance

And sleep patterns don't just affect young children; they also affect college students.

A 2018 study conducted by Northeastern Illinois University and UC Berkeley on more than 14,000 NIU students showed that college-aged students who attend classes that don't align with their sleep patterns receive poorer grades. For example, a "night owl" who has an early-morning class will perform better if class was later in the day. About 50 percent of students in the study took classes before they were fully alert, and 10 percent had mentally "peaked" before classes even started.

“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 co-lead author Benjamin Smarr.

The same could be said for people who are early-risers but have classes at night. However, people who tend to stay awake later seem to be the hardest hit. “Because owls are later and classes tend to be earlier, this mismatch hits owls the hardest,” said Smarr. “Different people really do have biologically diverse timing, so there isn’t a one-time-fits-all solution for education.”

The study notes that the best solution would be to have class day schedules closely resemble non-class days.

What about home-schooled kids?

As a home-schooling parent, I was curious about the results of this study because the assumption is that it is the random bedtime that makes kids cranky. But what if your kids have a random bedtime but still get a regular amount of sleep each night? I am curious to know if these results would still stand. It's possible that it's the randomness of the bedtime that makes kids cranky. But I would argue that it's the irregularity in the amount of sleep that's causing the problem — and that's not the same thing.

I certainly concede that most kids in the developed world have to get up at a regular time each morning for school. But there are also plenty of kids who don't. It would be interesting to know if any of the 10,230 kids involved in this study were home-schooled and if so, how the irregular bedtime affected their behavior - if it affected it at all.

For instance this study, conducted by researchers at National Jewish Health in Denver, Colorado, looked at the total amount of sleep that kids got each night and how it affected their ability to learn. Of the 2,612 students evaluated, 500 were home-schooled. And the study found that these home-schooled students slept an average of 90 minutes more per night than their peers. Overall, the study found that 55 percent of kids who were home-schooled got the optimal amount of sleep each night compared to 24.5 percent who attended a traditional public or private school.

I know it's a fine point and one that really doesn't matter when your kids have to get up at the same time each morning. But for those kids who don't, I think it's incorrect to assume that it's the randomness of bedtime that is the issue.

Editor's note: This article was originally published in October 2013 and has been updated with more recent information.

Which is worse for you, a random bedtime or getting less sleep overall?
One study that looked at kids' sleep and behavior patterns might have missed the bigger picture. Another study looks at academic performance.