Son is failing 2 classes

My son is completely failing 2 classes. He most likely won't be able to bring them up to passing before school is out. He's failing them U.S History and English 1 for the same reason. Participation. Most of what they do is class discussions. He's very very VERY shy. He has 1 friend and it's been his same friend since 2nd grade and they don't even go to the same school anymore. He's never made another friend. He doesn't really talk even at home. He's quiet. If people try to talk to him he will stutter and just scoot closer to me. He was supposed to do an oral report for English on a book they read but he tried and couldn't get any words out and ended up running back to his seat. He got an F on that. He will most likely have to redo that classes next year. But he will most likely have the same problem. IDK what I'm supposed to do. He's always been a very shy boy