Yankeelvr:
Sounds like a business opportunity! I will rent my gun for $1/MPH....how hard do you want your son to throw?
I will adjust it before I send my gun to you. $1/MPH. I will make him the first 110MPH 13YO!
To answer Dman's question my son was only gunned once before HS at a travel team try out. The coach borrowed one just to get a reference. 13U kids were throwing 62-69. Most HS freshmen are 65-75, with lots of 70's.
Always remember the Dad-7 rule it is very accurate.
Most people do not have the eye to really know how hard someone is throwing. I collect speed data for my sons HS team and it takes me a while to judge velocity. About 1/3rd of the way into the season I get a pretty good eye from behind the plate, I am usually within 2-3MPH, but when I get off to the side I can't tell very well.
Don't dread HS ball it is a great time, if your son loves baseball he will get it 6 days a week, really nothing better.
Have a great season!