Hi CA mom,
In your OP you said
He's learning a lot in PE (his teacher is into anatomy) and also has Spanish and Music which are new for him.
This seems like actually a lot for a young kid to have that is new. If there was absolutely nothing new for him or if he were not happy, I guess I would do more. But since he is happy and he has some areas he likes, I think you're likely to be fine. I also think that even when he isn't being taught anything new, he may still be learning a lot. DS learns a lot about how kids get along and group dynamics and how things are explained. These are intangibles, but I think are helpful things to know. If he weren't happy, he probably wouldn't notice these things, but since he is, he may be getting a lot out of school that you may never know about.