I would say talk to the teacher about this and find out her inpressions. Is he bored or seemed bothered at school. Also, talk to your son more and show your empathy for the situation. I think when kids feel understood that goes a ling way. It' a new year and my kids take a good month to get in the groove. I hope this helps.
OTGMom, thanks for the reply. I've emailed his teacher to get an accurate read on how much time he's really spending outside the class. I know that DS won't show he's bothered or bored at school. That's not his style.
DH and I talk with DS pretty much daily about his feelings, because he needs a lot of help to work through his thoughts and anxieties.
While I'm hopeful this is just the beginning of the year jitters, I worry that it's become his routine. I think DS may have had this same habit last year as well. There were A LOT of days DS would bring home a bunch of worksheets and say he had to do them as homework because he was in the bathroom when the rest of the class did them as classwork. Frankly, it just didn't hit my radar until now.