@mathmom thanks for that clarification. I don’t think he would have any problems having his school say that his schedule is rigorous.
I am confused however as to the progression into AP classes as you say so many students in the US seem to take AP courses before senior year. I can see how that can work in the humanities and social sciences, but how does it work in math and sciences? Presumably you can’t take AP Calc BC before doing all the prerequisite work in the grades leading up to it? He surely needs to complete the grades 9-12 math sequence before doing AP Calc BC? The same goes for physics and chemistry? How can he do AP Physics 1 or Chemistry before having completed the grades 9-12 science curriculums?