If you throw 75 max that is probably average. If you throw 75 consistently that is a bit above average.
For comparison here is what our JV pitchers throw:
(I've ranked them by current effectiveness in my opinion, not by velocity)
1. 70-72, 75 max 16yo soph.
2. 77-78, 79 max 15yo soph
3. 78-79, 81 max 15yo fresh
4. 78-79, 80 max 15yo soph
5. 73-74, 16yo soph
6. 77-78, 79 max 15yo soph rehabbing from 6 week injury layoff
7. 71-72, 76 max 15yo soph rehabbing from 16 month injury layoff
I expect #7 to be the hardest thrower once he completes his rehab.
This is a slightly above average JV staff, but certainly not the best in our league. Our league is one of the best in the nation, if not the best.
During our winter and preseason games other than 1 JV team that had a pitcher working at 81 and throwing 83 or 84 max with good breaking stuff most of the JV pitchers I've seen from other teams were throwing low to mid 70s. One JV team in our league has a 15yo freshman pitcher who works low 80s and hits mid 80s. They've got 5 varsity pitchers throwing mid to high 80s or above.