I don’t think that anybody has done a comprehensive list of policies for all 37,000 US high schools, but IME, many do not require students to take AP exams. And within a HS, some classes may require the AP exam to be taken, while others don’t.
Regardless, that was not the OP’s question; I assume s/he knows whether the HS requires the AP exams. Obviously if a HS requires them, then the student should take them. But if the HS doesn’t require, then it really does not matter other than for college credit.
There is no “game” to be played here. The kid/parent has already sent in the enrollment deposit by the time AP exams roll around.