I think at this point in time I would go with "if it ain't broke, don't fix it..." If he continues to be happy, then I'd leave it alone.

That said, I'd reevaluate a few weeks in and see how he's doing - still happy? then no problem. Hating school suddenly - I'd set up some time with both teachers, as by then they will have gotten to know him and be better able to relate what you say to the child they know from class.

Good luck! Not an easy situation.

“...million-to-one chances crop up nine times out of ten.”
-Terry Pratchett