What is the typical course schedule for a freshman at your H.S. How many periods in the day? And what are the minimum requirements. Personally I think it's a lot to take those three AP's as a freshman. But you know your kids & school better.
Which AP Physics are you talking about him taking.. AP Physics 1 Mechanics or 2 E&M? Or AP Physics C with Calculus. What classes are offered at your school.
At DS's H.S. they do not allow ANY AP's freshman year, with the only exception of the rare kid who take AP Calc BC as a freshman. And AP CS could be taken in sophomore year but not freshman. There are required classes and limited time to take them like English & Social Studies, and PE.
My son is a senior and taking AP CS & AP Physics 1 & Physics 2. He's currently sitting the Physics 1 test & takes the other tomorrow. It's a lot of work.
If your son is done with pre-calc would look into taking the Math II SAT in June or next fall. It's designed for after pre-calc. There is no Calculus on that test at all.
Do you have a plan of math after freshman year?