My mother asked me what I did/learned at school every day, and my response from K-12 was always "nothing". I often said I wanted to stay home, but I probably wouldn't have liked that (I am an only child and I would have been bored at home too). I am certain that I learned something at school - I'm pretty sure that I did not enter K knowing calculus.
I did not have any language issues but I was similar to your DS. Back off of the questions for a while - maybe he'll come home one day and let you know what happened at school (I typically reported what the "bad" kids did).
