It is the parents responsibility to protect the health of the player. I have told all my sons that if you do not feel "healthy" and ready to go out of the bullpen then you do not pitch. If you feel during the game that you are fatigued out and need to come out, call for a mound visit. Of go over your pitch counts with the PC between innings.
As far as the coaches are concerned, most know when the player is "losing" his stuff. For my sons, when they start losing their off speed control I can tell it will not be long. I wonder if the stories I hear about kids throwing 100+ pitches are pitchers from smaller schools with limited roster size? We generally carry enough pitchers so no one gets worn out.
2018 has been told he will get varisty innings this season. He is crusing 85 and hitting 87 I have already had a "hey what are you planning for 2018 this season" talk with the HC... Now this might be easier for me having had three others come through the program.. Some might think that I should not talk to the HC about his plans, but he's my son, he gets one shot, and he is very talented. If I felt the HC did not have my sons best interest at heart we would play elsewhere.
I think you are correct about the smaller schools. Last year we had 4 pitchers, including my son, that could keep the games close. This year we are down to 2 pitchers with 4 others that can throw strikes but will need more defense to keep glames close.
So are there other high schools nearby where you could bring your son if you felt your son's pitching health was in danger? And would your son have to wait a year because of UIL rules to get back on varsity at another school?
I will post an update after I have a "what are you planning for my son this season" talk with the HC.