D.D.
My daughter is going through this with my 2nd grandson right now. I'll give you the same advice I gave her.
The more of a big deal you make out of the separation the more he'll feel anxious about it. When you drive him there and drop him off do so cheerfully and express to him what fun it'll be to do new things. Get him settled and leave.
If you are told that he was crying or anxious don't decide to discuss the whole situation with him. Some little ones take to a change in routine well and others take a little while. As long as you keep a positive attitude he'll pick one up too.