That's the key finding of new Australian research that reveals the true importance of bedtime.
The study of 3600 Australian children from the Growing Up in Australia study has found that getting them to bed early may be even more important than ensuring they have a long sleep.
The findings were presented at the Australasian conference Sleep DownUnder 2015 in Melbourne in late October. Children participating in the study, the largest of its kind, were questioned three times in their first nine years of life, at ages 4-5, 6-7 and 8-9. They were divided into four groups - those who were early to bed and early to rise, early to bed and late to rise, late to bed and late to rise and late to bed and early to rise. Kids who were early to bed were asleep by 8.30pm, while late-to-bed kids fell asleep after this time.
"This is valuable information for parents, many of whom will know about how important it is for their kids to get lots of sleep overall but not much about how significant the bedtime itself is," says lead researcher Dr Jon Quach, of the Murdoch Children's Research Institute and The University of Melbourne in Melbourne.
Results show children who are early-to-sleep have better health-related quality of life, and their mothers have improved mental health, compared with children who are late-to-sleep. These benefits were seen in all early-to-bed kids regardless of whether they woke early or slept late.
Other South Australian research presented at the conference was able to conclude that being early to bed and early to rise may trim the waistlines of older children. Results from 2200 children aged 9-16 showed adolescents who went to sleep late and woke late had higher BMIs than those who fell asleep earlier and woke earlier, even if they had the same amount of sleep overall.
"The late sleepers were considerably more likely to be obese, have a poorer diet, get more screen time and less physical activity than other kids," says lead researcher Professor Tim Olds from the University of South Australia.
However, it remains to be seen whether bedtime influences weight or whether, as is more likely, obese teens gain weight thanks to a lifetime of unhealthy habits - like sleeping late and eating poorly - that all interact together, he says.
Taken together, these large Australian studies suggest that children's bedtimes have a deeper impact on their own and their parents' lives than previously thought.
Other discoveries presented at Sleep DownUnder 2015 to promote better sleep included a meditation technique, a diet rich in veggies and a pre-bed mug of milk extracted from sleepy cows.
Several other several studies revealed just how fatigued and sleep deprived many Australians are, particularly students and shift workers.
Margaret Evans has a background in teaching, journalism and publishing. She is the editor of NOVA Holistic Journal.