I found a great article from the new healthy living website from Children's Healthcare of Atlanta, Strong4Life.com. According to doctors, children in 5th grade need 10 hours (or more!) of sleep each night.
Let's say your child has to be on the bus by 7:15. He needs about an hour to fully wake up, get ready, and eat breakfast. That means he needs to be up by 6:15. If your child gets 10 hours of sleep, then he needs to be ASLEEP by 8:15.
Check out the article from the website here. It has some great information about the effects when children this age don't get enough sleep.