There was one kid at one of the area high schools a few years ago who ended up with a paralyzing injury to due to getting hit during a football game and landing wrong.
For some schools, football is the only sport. However, if you're in a larger school, there are probably more options than just football, which won't involve players slamming into each other. Basketball and baseball are sometimes other options.
Football probably isn't a good bet for a long-term career option any more because of all the heath data that has been coming out about it in the past few years.
It probably would have been better to have this discussion before your son started participating in the sport. It will be harder to get him out of it now if he still wants to continue to participate in it. Teenagers are invincible after all, and they don't always understand the consequences of things that can cause health problems later down the line.