Some kids don’t have the desire or need to socialize outside of school. Maybe by the time he gets home, he’s exhausted emotionally and needs to recharge in other ways. This is not a reason to worry or something that you need to fix or change; it very well could just be his personality and how he prefers things to be socially.
I think the best thing you can do is let him decide things friend-wise and if in the future he asks for help or support, you can provide suggestions at that time.
Parenting Coach, school counselor, mom of adult son with ADHD, author