L.N.
Your situation sounds just like mine did. Believe me, this will be harder on you than your little one. The first few times my girls were a little nervous, but now they love going to "school". My girls were allowed to bring a favorite toy to comfort them, does your son have a favorite toy? If so, you might send it along. Start prepping him today. Tell him he is going to big boy school tommorrow to play with the other kids. I have read that kids are more comfortable when they know what to expect and whats going on. Don't worry, he will be just fine and soon you will be amazed with all the new things he is learning.
-L.