Is This Normal Behavior For A Teenager?

I will keep it simple.

Someone I know has a son who is 15, sophomore in HS. Only child. Goes to a small private school. He is a big kid. Not fat my any means, he is just over 6' and not thin, just built big.

He played football in junior high. Not in HS. He started the year off playing basketball, but he quit. He said it was because of his grades. They were good enough for him to be eligible, but it is believed his mom is discouraging him from playing sports.

He does not talk at all. Someone who went pick him up last week told me he got into their truck. Didn't say hey or anything. They dropped him off. He didn't say bye, thank you, nothing. That person asked him if he wanted them to go somewhere to grab something to eat, or if there was anywhere he wanted to go. He just said no.

While that person was waiting for him at school, they get a call from his daddy who tells them "don't tell him about Will Wade" (it was the day he was announced he was suspended), he went on "I am going to talk to him about it when I get home"... WTF?

Outside of school he doesn't really hang out with anyone. His dad is his best friend. Doesn't do anything without his dad.

Would you be concerned about a kid like this?