Can someone give me any tips on what I need to do.

I have a 5 year old in kindergarten and I’m starting to receive notes from the teacher saying that my son is behaving bad not sure exactly what he is doing but the other day the teacher sent school work with written on it “He didn’t do his work because he was playing”. My mom picks him up from school since I work and yesterday the teacher told my mom that he wanted to talk to my husband and I. I called the teacher today and left a message with the front desk to have the teacher call me. I had this problem with my son last year too. I really don’t know what to do to make him understand that he needs to listen and behave.
I have tried taking his stuff away for a week and it usually works but as soon as he gets his privileges again he starts acting this same way. I know he is just a child but he is already 5 and old enough to understand that he needs to behave. Anything please?