There is quite a lot of evidence in your description that he is not really unhappy in his school setting—he is fine when your husband picks him up, talks a lot about his school, etc. So I wouldn’t worry too much. And I’ll tell you a little secret, Angie: sometimes kids do that because they think their mothers will be unhappy if they don’t! It sounds as though he recovers after a brief adjustment period once you leave. If the school has an observation room, stay for a while and see for yourself how long it takes him to settle down after you leave.
Another useful trick is to select a special toy once or twice a week that he can take for show and tell. That will help him look forward to getting to school. Also each morning I would rehearse with him the day’s schedule—“Mommy’s going to take you to school and Daddy will pick you up and bring you home.” And talk to the director about whether he could call you on the phone once during the day if he seems upset. Finally, talk to him about why he cries; you might be surprised at how articulate he can be.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.