The Washington Post Challenge Index measures a public high school's effort to challenge its students. The formula is simple: Divide the number of Advanced Placement, International Baccalaureate or Cambridge tests a school gave by the number of graduating seniors. Tests taken by all students, not just seniors, are counted.
The rating is not a measure of the overall quality of the school but illuminates one factor that many educators consider important and that can favorably affect other factors.
Clarke County in Clarke (Berryville, VA)
| RANK | YEAR | INDEX | E&E % | SUBS. LUNCH % |
| 3 | 2008 | 5.061 | 0.80 | 0.13 |
| 3 | 2007 | 4.535 | 82.00 | 13.00 |
| 13 | 2004 | 2.880 | ||
| 18 | 2003 | 2.500 | ||
| 20 | 2002 | 2.230 | ||
| 23 | 2001 | 1.790 | ||
| 23 | 2000 | 1.600 | ||
| 24 | 1999 | 1.550 | ||
| 11 | 1998 | 1.260 |
Thomas Jefferson High School for Science and Technology in Fairfax County, with a rating of 7.575 and an Equity and Excellence rate of 100 percent, was not ranked because it is a magnet school with a selective admissions police and an average SAT score, 2214, higher than the highest average for any regular enrollment school in the country. The index is designed to show which schools are challenging average students and does not work well with schools such as Jefferson that have few or no average students.
Briar Woods and Freedom in Loudoun County, Clarksburg and Northwood in Montgomery County, Dr. Henry A. Wise in Prince George's County and North Point in Charles County were not included because they are new schools and did not have full senior classes graduating this year.
