Currently in Schenectady, students need to be recommended by a teacher for an AP class. It would be interesting to see the statistics on the percentage of graduates who passed one or more AP exams. Schools in Maryland and Virginia have increased their AP participation by abandoning a "gatekeeper" mentality that created limited access for a small cadre of top students and by recruiting minority students.
http://www.washingtonpost.com/wp-dyn/content/article/2009/02/04/AR2009020401459.html