In HS I sat behind the same kids I played ahead of on every other team. I was a 16yo senior while they were 16yo sophmores and juniors. I wasn't good enough at 16 to be a major contributor to the team and the coach didn't have any incentive to develop me for the next year. It can be tough on a kid but all he can do is work at it as hard as possible and try to earn playing time.
Don't quit. A young man's time in baseball is almost always too short. Enjoy being on the team, playing with friends and becoming a better baseball player.
Although it is rare, he could still play at higher levels. We had a light hitting catcher in HS who went on to hit over .350 in JC ball and eventually played professionally.