My athletic 12 yr old son has dreamed about playing tackle football all his life. He played quarter back for 3 seasons of flag football and kept asking to play tackle. I signed him up this year and after the first practice he wants to quit. He says only 6 players haven't played tackle before and "he sucks." I want him to play the season or at the very least try it a month before deciding. I told him this and told him he needed to go to practice today. He refused to get out of the car. He is strong willed but this is the first time since he was a toddler that he has been out right defiant. How to proceed?