I have the same issues, and my son has struggled. Reaching out to the school helped with support for both my son and myself. There are some good resources online, however consistency is they key. A routine when they come home has also helped (even if just playing his favourite song and dancing in the kitchen) he know that he is with me and rules apply. We also drew up some house rules together. It’s really hard but, but stick with it, your son will thank you for later in life for being his constant
