I went through HS in the mid 70s. I was not brought up in that over the top baseball culture but knew some guys who were. I knew a kid whose arm was always sore, 24/7. In little league he far and away threw harder than anyone else. His dad was his coach and pushed him relentlessly year after year. He went on to a different HS so I don’t know how things turned out for him after that, but he was throwing max effort heaters and curveballs in little league. I got hit by one once and it was no joke.