Not sure why the "AP exam" thing is being singled out as opposed to, say, each child being bought a car? Read the title of the article again.
The AP tests are one of the most effective ways to achieve their goal: an exam fee being maybe $100 and a uni course being probably > $1k; the additional scholarships that are accessible to people with the GPA boost that AP courses give.
And besides, the AP courses in a typical high school are pretty "core" I'd say - a capable student should learn biology, history, some foreign language, even(!) basic comp sci. With American standards in education, I'd actually consider the AP courses to be "standard" level for an intelligent kid. If they don't like the subject, then more power to them - they can avoid it in college (which again, saves money).