I am so sorry your family is having to deal with people like this during what should be a joyous time. The same thing happened to my nephew when he was a Freshman...
Please tell him to hold his head up high...he has done nothing wrong. If his "friends" and other parents can't be happy for him and proud to have such a successful player on the team than that is not his problem. If things continue to get worse, I would have a meeting with the school...
The green eyed monster is an ugly beast.
ETA: I should have read all the posts...1st one had me fuming so I had to respond ASAP.