Hey, nice to see you‘re willing to help. How about you try to find something he likes and talk to him about it? I think this might help him feel more comfortable around you and then you can proceed to talking about his grades and all. When I was in therapy I had a really hard time speaking and getting my feelings out so my therapist would play Uno with me and ask questions so it all didn‘t feel so weird. I know you‘re supposed to tutor him, but I think gaining confidence is very important at the moment.