Hi kksann,

That does sound intense although at his age it may be just fine for your son to work for that longer stretch.  If you're concerned I'd think about talking to your son's teachers or the principal - maybe at back to school night - to learn more about the schedule.  It could be that while there's nothing on the printed schedule, the teachers do build in quick stretch breaks or other things to break up the learning time.  After all it's in their best interest to keep the kids focused, alert, and ready to learn!  

If he's changing classes, even the five minutes he has to walk from class to class may give his mind a chance to clear and refresh itself and will give him a chance to stretch and move his body a little.  Eating a healthy snack sometime during the morning will also give him a little extra energy boost.

Aside from a chat with the school, I wouldn't take any action right away.  Keep an eye on your son for a couple of weeks as school's getting started and then talk to him about the schedule.  If he says he's having a hard time focusing all morning then you could think about talking to his teacher(s) or the principal about ways to address the issue.  If your son starts to struggle, it's unlikely he'll be the only one.

Good luck!

Kat