danny lieu is the associate medical director here in d.c. he says it's not just about how long your children are sleeping but also what time they'reoing to bed. >> we tend to think about only duration, but it's really critical to think about when we're sleeping as a critical mponent of sleep health, mental health, learnial, physhealth. >> children's national is par a publish research on optimal bed times based on a child's age. it builds off recommendations that many parents already use from the american academy of fe ed yac. guidelines call for babies to sleep from 6:00 p.m. to 6:00 a. with several additional hours factored in for nap. toddlers should go to bed around 6:00 p.m. andesprchoolers should aim for a 6:30 bedtime getting 11 to 13 hours of sleep. get them in bed by 7:30. they need about 12 hours of sleep and should avoid taking naps. 8 to 12-year-olds may not be ready for bed until 8:00,while teenagers just aren't wired to go to sleep until 9:30 or 10:30. dr. lewen says the key is suven in the er, or it can lead to a phenomenon cal