My high school wasn't on there, but I have to agree with tar heel that the criteria is faulty. Two of the schools listed in my state pay for their students to take AP tests, but my district didn't.
Moreover, my school encouraged students to take actual college classes (Concurrent enrollment) at OU, UCO, or any of the local community colleges more than they encouraged AP classes and tests. I think something like 30% of my graduating class had credit from OU or Oklahoma City Community college when they graduated from high school -- many of us had more than a semester's worth under our belts, too. Plus, the very advanced programs in our high schools (AEGIS Math and English, both extremely selective two year programs) weren't necessarily AP classes. The option to take the tests were always there, but few people did since it was just as easy (and cheaper) to take an advanced standing or CLEP test at whatever college they were attending.