I actually think you have good reason to be concerned. My son was very similar sounding to yours. He did like his K teacher and that year went ok, despite not learning anything academic. First grade did not work and we started homeschooling him.
He did make a few friends at his neighborhood school who he continues to see. So, it wasn't a complete loss, but he did also acquire a dislike of all things "school".
We thought we were sending him to school for the social aspects and to learn to "do school", follow instructions in a group, wait in line, participate etc.
There are many ways of learning those skills that are more effective than being at school, in my opinion. I didn't see any other way except sending him to school until I was forced to try the alternative. You may end up enjoying homeschooling him, he sounds delightful!
