my kids have the same problem, (ds 9yrs, dd 7yrs) ds can't stop thinking about things and dd has growing pains,and/or lays awake "just thinking"
What time does he get up in the morning?
Some things that have worked for me when I can't sleep are turning the light on (dim) and reading for a while. Listening to soft music so I can relax and fall asleep. And sometimes I just have to listen/watch a tv show. I usually pick something from the history channel or discovery kids. It gives my mind something else to think about rather than what it is stuck on. When I was in my late teens I bought myself a little tv that had sleep timer on it and I'd put that on so I didn't have the tv on all night. I really just needed it for a short period so my mind would stop spinning. A good friend would write in a journal, make notes so she wouldn't forget to do something the next day and by putting it down on paper allowed her to let it go from her mind.
Has he giving you any reason why he can't sleep?