How can I deal with this???

I am the leader of our sign language group in my church. A new youth leader has been appointed, and I can't stand him! I know that sounds terrible, but he just will not cooperate! We are supposed to be working together, but he just will not. He is childish and immature, and he constantly undermines me. I have smiled and gone along when he changes programs and schedules without talking to anyone about it, he has cancelled standing scheduled events that were planned b4 he was put in his position, and not he is goofing off in my sign language groups. He is 21, but acts 10. He laughs at the kids trying to learn sign and he moved a scheduled concert up one month to accomodate himself! I'm at my wits end! I know my feelings are quickly turning wrong. I have spoken with the pastor, but it seems to have fallen on deaf ears. I've even thought about resigning and finding a new church. I really need prayer for God to help me (and him) in this. Should I leave, quit, or let him keep running over me