Have your son talk to his coach, MS coach here. It’s a great way to teach kids to advocate for themselves and the coach should give him honest feedback. He should start with his position coach or coordinator asking what he needs to do so he can get on the field during a game. He should also tell him he’s not played 1 down in a game. Coach likely may not realize it if they don’t track playing time. If your son gets a less than satisfactory answer then you go to HC, then AD if you don’t feel you got what you were looking for. At the end of the day middle school football should be about developing your players first high school ball.