Fifteen years ago, when I discovered that many good high schools prevented average students from taking demanding courses, I thought it was a fluke, a mistake that would soon be rectified. I had spent much time inside schools that did the opposite. They worked hard to persuade students to take challenging classes and tests, such as Advanced Placement, International Baccalaureate and Cambridge, so students would be ready for the shock of their first semester at college, which most average students attend. The results were good. Why didn't all schools do that? I still don't have a satisfactory answer. It always comes up this time of year because of my annual rankings of public high schools for Newsweek, which is based on schools' efforts to challenge average kids as measured by participation in AP, IB and Cambridge tests. Many school superintendents and principals who run schools that restrict access to those college-level courses and tests have disappointing results on the Newsweek list. Some of them object to my methodology. It is clear from my conversations with them that they are smart and compassionate people. But after seeing what has happened in the Washington, D.C., area, where all rules barring admission to challenging courses have been removed, I think the dissenters are wrong and should take a look at what educators are doing here. In 2008, Newsweek received a letter from the superintendents of 39 small districts in New York, New Jersey, Connecticut, Illinois and Massachusetts, declining to provide data for their schools. If Newsweek already had the numbers, they asked that the statistics not be used. 'We all believe that all schools, communities -- and your readers -- are poorly served by Newsweek's persistent efforts to use a single statistic, the number of students who sit for AP or IB exams, to rank schools,' they said. This year, the protest was smaller and less organized, but I received some e-mails making the same point. Howard Smith, superintendent of the Williamsville Central School District in New York, said the Newsweek list had 'limitations with respect to the assessment of school quality and reflect only a portion of what we do.' Tony Pavia, principal of New Canaan High School in Connecticut, said 'judging a school based on one simple factor such as AP tests makes absolutely no sense, especially since it implies that anything other than AP students, AP classes and AP tests is essentially irrelevant to a school's quality.' Both last year and this year, I contacted the protesting superintendents and principals and asked them to treat our request for their data as a freedom of information submission. They were all professionals, just trying to make a point, and quickly agreed to send me their numbers. In return, I promised to publish their objections to the list and keep alive what I consider a very useful argument. The lists' critics are right about its narrow scope. Schools are rated by just one number: the ratio of college-level tests taken each year to the number of seniors graduating each year. As I have said many times, that narrow simplicity is useful for readers because they can understand exactly what I am doing, calculate their own ratios for any schools outside this area, and argue with their friends and me about the result. Parents use the list to compare schools, exactly as I intended. That produces some useful insights, such as why there are so many schools with similar student bodies that do considerably better than many of the protesting schools. New Canaan High, for example, has an AP participation rating of 1.230. That puts it in the top 5 percent of U.S. schools, but there are 120 schools in the D.C. area with better numbers. Langley High School in Fairfax County, Va., with 7 percent low-income students, is demographically similar to New Canaan, where 2.4 percent of the students are low-income. Yet Langley's AP participation rate is 3.807, three times as large. One important reason is that New Canaan, unlike Langley, prohibits students from taking AP courses if their grades in previous classes weren't good enough. It does not matter how much they want to take the course or how hard they are willing to work in it. Pavia, the New Canaan principal, said, 'I do not believe that AP classes are for everyone any more than physics or band or ceramics or football is for everyone.' Washington area superintendents and principals have a different view. They think every student who wants to get a taste of college trauma in an AP or IB course ought to be able to do so. They tell me their open door to AP, IB and Cambridge courses raises expectations and inspires better instruction in lower grades. The number of students passing the exams remains very high, despite letting so many more students take them. 