K..
You've done all you can do. You can't force him to be ready, or want to start. Whose idea was it for him to go, in the first place? Someone who is "excited" and "motivated" would've already been in school for a while, IMO. Either he is not ready, doesn't want to go, or is sick of being asked about it, is my guess.
In any event, I think you've been as supportive as possible. Leave it alone for now. He has to go because HE wants to and is ready. Not because anyone else wants him to.