I agree with the overall tone of the previous posts... usually can't control what HS you go to and most exposure is had via travel/showcase.
However, I will add a few "however"s
When we got our program turned in the right direction, there were more opportunities for players who wanted to play beyond HS for many reasons... the goal became perceived as more attainable because more went before them, more college coaches did take notice of the program (at least locally), more college coaches who wanted a look at an opposing player would not scratch our game from the potential "go see him" games - they would rather see their guy perform against decent competition if possible, players have more confidence that they are working under HS coaches that can help them get there, etc.
More importantly for your son...
If son is a college prospect, he should have some influence in many ways to help the HS team improve. He will need to have a certain skill level that will help keep his team competing when he is on the mound, regardless of what is going on around him. He will need to have a certain work ethic and composure which is likely to rub off on his HS teammates, eventually helping raise the level of the group. He may be scrutinized by prospective RC's as to how he handles the adversity of playing with a weaker HS team.
There are great opportunities for a young man faced with this scenario. While perhaps not immediately evident, it can be very rewarding.