Exactly, my son who is 5'7" and weighs in at 145 pounds throws low 80s and he just turned 16. He struggled with his control, but he never got into trouble because, even though he walked runners, no one really got any hits off him.
Now, he's only walking about 1 for every 4 Ks he gets. The kids are starting to hit his fastball, but he keeps them off balance with 2-seamers and curveballs for the 1-5 hitters due to the good movement he gets, and he throws strike one curve balls for the 6-9 guys who he then slips his 4-seamer past with ease.
His arm is also conditioned to throw 100 pitches without even thinking about getting tired.
I have total control over his mechanics, much to the chagrin of the up, down, out HS coaches you are referring to. I just tell them that my will is stronger than theirs and that they can sit my son at their own expense, but if I have to throw a long bullpen with him because he doesn't pitch, then he'll be lost to them for the next several days. That also gets him his innings on schedule. They hate my guts, but I don't give a sideways crap about what's on their minds.
I just keep pointing out to them, "Show me a kid on your staff who follows your mechanics and your time tables and throws harder than my son." The conversation ends right there. I then offer to teach that coach's pitchers for him and he walks away.
I'm such a tool when I need to be.