Often such feedback from day care or pre-school is worth listening to, because those folks (if they are seasoned) have such a range of experiences from which to draw. It can be hard to discern at times what might be difficult but nonetheless 'normal' behavior vs. symptoms of a disorder. Here's what I'd suggest: (a) obtain details about your son's functioning at school; the particulars are important; (b) have a consult with a child mental health clinician who can both 'eyeball' your son and have a discussion with you about him.