2005: 345, index 1.850
2004: 168, index 2.044
2003: 157, index 2.044
Jay Mathews's Challenge Index ratio is based on the number of Advanced Placement (AP) and/or International Baccalaureate (IB) tests taken by all students at a school, divided by the number of graduating seniors for the year previous to that list's publication.
Mathews does a Challenge Index for Washington, DC area schools annually; washingtonpost.com: Challenge Index (free registration required) has those results back to 1998.