The rankings are based entirely on the single criterion of how many AP (or two other similar) tests are taken by the students in the school. That's it. How the students perform on the tests is not part of the equation.
Newsweek's description: "Public schools are ranked according to a ratio devised by [reporter/editor] [TP Ed. - and "doomed fad" expert] Jay Mathews: the number of Advanced Placement, International Baccalaureate (IB) and/or Cambridge tests taken by all students at a school in 2008 divided by the number of graduating seniors."
Just wait until you read what Grannan then reports about the ties between Newsweek, Mathews parent-paper: the Washington Post, and the test-prep industry. Hint: WaPo owns Kaplan.
You'd think these big-media folks would have figured out by now that we're living in the age of instant global communication and real-time search. I guess they still think us bloggers are as lazy as their reporters.