The editor of the Fairfax Extra asked me to do something different for this column. He wanted me to comment on the latest SAT scores instead of answering letters.

Previous editors who have asked me to write about the SAT have had to endure a venomous rant from me, a longtime SAT hater. Average SAT scores are a stupid way to measure schools, I told them. All that those numbers tell you is how much money and education the parents have, on average, and they say little about how hard the school is trying to make its students better.

If the editor was too polite to cut me off at that point and tell me to go do my job, I would move into second gear and insist that The Post end its annual reports on how local schools and districts have done on the SAT. I was about to unleash this rusty diatribe on my editor when a thought occurred to me. Why not use this opportunity to see if I was actually right? I had the new SAT scores for each Fairfax County high school, and I knew the percentage of students who qualified for federal lunch subsidies -- the standard measure of poverty in schools -- on each campus. I could compare the two figures and see what they revealed.

Please note the charts that accompany this column. One ranks the schools by SAT score, the other by percentage of low-income students. Each of these measures has its problems. SAT tests are not taken by all students, just those who want to go to college, and changes in participation rates can affect the average score. The percentage of students who qualify for lunch subsidies is often understated, because some low-income teenagers think the program carries a stigma, like wearing your dad's old sneakers. And the income figure does not tell me what percentage of students have parents who have decent incomes, but not much education, another factor when assessing SAT score averages.

Since this is a column for reader comments, I welcome any questions or thoughts you have about what you see here. I think the charts back up my view (which is influenced by social scientists who have done much more sophisticated research than this) that SAT averages correlate closely with parental income.

Most of the schools on the SAT list are close to their places on the low-income list. Two that have very different rankings on the charts are Stuart, 18th on the SAT and 24th on the income chart, and Hayfield, 19th on the SAT and 13th on the income chart.

Stuart is an extraordinarily diverse school with a strong International Baccalaureate program, and it has many students from immigrant families that may be poor but place a strong emphasis on education. That could push their test scores higher than the income chart would suggest. Hayfield could be one of those schools that have a large number of parents who have decent incomes, but less education, which can be a factor in SAT averages. I don't know and will have to investigate further. The differences could just be anomalies, and in honor of all those statistics teachers who have pounded the point into me, I should also say that correlation is not causation.

Nonetheless, I am fortified in my belief that the SAT average is not worth much, except to people who like the idea of sending their children to schools that have many students with affluent and well-educated parents. There is nothing wrong with that, but it doesn't tell us much about how good the principal and teachers are. For that I would prefer to look at each school's participation rate in college-level courses, the length of its principal's tenure, the experience of its teachers and the percentage of its seniors who go on to graduate from college.

We know that every high school in Fairfax County ranks in the top 3 percent of all U.S. schools in participation in Advanced Placement and International Baccalaureate tests. We know that every one of the high schools has many great teachers, classroom equipment that is the envy of other school districts and a critical mass of students competing for places in the most selective colleges.

That means that whatever your children's dreams or talents, they are going to get plenty of encouragement and stimulation in any Fairfax County high school you choose, and there are few school districts that can say that.

Please send your questions, along with your name, e-mail or postal address and telephone number to Extra Credit, The Washington Post, 4020 University Dr., Suite 220, Fairfax, Va. 22030. Or e-mail extracredit@washpost.com.