Your son has a great arm. That is an understatement. Congrats! I have had some great arms come through my hs program over the years. We have been very fortunate in that respect. Just to give you and idea of how they progressed.
Matt Harrison LHP 6-4 195 as a freshman 78-80
Sr year 6-5 210 89-93 3rd rd pick Atlanta
Starting rotation for Texas Rangers
Chris Luck RHP 6-2 160 as a freshman 86-88
Sr year 6-3 178 88-92 20th rd pick Tampa
Pratt Maynard RHP 5-11 190 as a freshman 83-85
Sr year 6-0 210 88-91
Soph at NC State Catching and infield
Josh Darroach RHP 5-11 185 82-85 as a freshman
Sr year 6-0 200 85-88
Mt Olive Freshman
Antwain Evans RHP 6-1 190 82-84 as a freshman
Sr year 6-3 225 85-87
St Augustines college
Shelton Moore RHP 6-4 230 84-85 as a freshman
Sr year 6-5 255 90-93
NC A@T
Curt Watkins
5-9 140 75-78 as a freshman
Sr year 85-88 as a senior
Lenoir Comm College
There have been more. The common thread in all of the guys that came in with above average arms that left with outstanding arms and the ability to pitch at a high level was their work ethic in the off season. Make sure your son continues to work very hard on his mechanics. Works very hard in the off season to improve on his conditioning , core strength , arm strength etc. Make sure he doesnt get over used because this can happen to a kid with an outstanding arm.
The future looks bright for your son. I look forward to keeping up with him and his progress. Good luck