I always say “please” and “thank you.” I tip at least 20 percent. I never abuse editors or waiters. Many people have told me that I am a nice guy.

So why do so many private schools these days treat me like a loathsome intruder? They don’t actually say they wish I would drop dead, but it is clear that they don’t want to hear from me. I am asking them for information — how many graduates and Advanced Placement tests they had last year — that they consider none of my business. Thousands of public schools have provided the same data to me for the past 14 years.

For the first time, I am including a sampling of private schools in my annual high school rankings, just posted. Most people think the main difference between public and private schools is that the latter charge tuition, sometimes exceeding $30,000 a year. That’s true, but there is also a great gap in accountability to the public — particularly for parents trying to find the best school for their children — because most private schools withhold vital data about their academic programs.

Since 1998, I have prepared a ranked list of public high schools based on what I call the High School Challenge Index. I divide the number of Advanced Placement, International Baccalaureate or Advanced International Certificate of Education tests at each school by the number of graduating seniors. If the school’s participation ratio is 1.000 or higher, it goes on the list. Only 9 percent of U.S. public schools have reached that level.

Many parents and educators have told me that they like the list. It ran in Newsweek for several years and now appears on The Washington Post’s Web site. The parents and educators say the list is easy to understand and indicates how hard a school is trying to involve as many students as possible in programs that provide a bracing taste of college academic demands. Some also say they like the fact that I am not rating schools by test scores, because differences in test averages between schools are more a sign of differences in family income than educational quality.

Other people, particularly educators in wealthy neighborhoods and in private schools, say the index is simplistic, unfair and deceptive. They say their schools’ best qualities cannot be captured by a number. They say I am taking advantage of the human fascination with pecking orders in order to pump up our page views.

When I started the list, I thought I would never get any data from private schools and didn’t try. The National Association of Independent Schools urged its members not to cooperate with me. But many readers asked me to include private schools, and a few of those schools volunteered. So this year I said, why not?

I wanted only a sampling. I contacted or searched the Web sites of about 200 private schools across the country and got the data I needed from 30, including President Obama’s alma mater, Punahou. I rank them here but emphasize that they are all in the top 6 percent of American schools measured this way. They are exceptional schools, not only because of their academic rigor but also their willingness to share their data.

With this analysis, you can make interesting comparisons. Andover and Exeter are alike in size of graduating class and prestige. But Andover (based on an estimate using its 2010 data) has a much higher AP test participation rate. This may reflect Exeter’s decision to deemphasize AP in favor of home-grown courses. Some parents and students like a heavy AP environment. Some don’t. Such information helps them, but most private schools don’t provide it because they don’t think it’s important or don’t want to be compared with other schools.

Take Sidwell Friends, the prestigious private school in Northwest Washington. The number of AP tests it gave last year is a secret. School spokesman Ellis Turner said that information and other data are shown only to colleges to which its students have applied.

This is common among private schools. Instead of data, their Web sites offer press agent prose. On the Sidwell Web site, Upper School Principal Lee Palmer says: “[O]ur teachers understand that a student is a whole human being whose value is not tied to the grade on a report card. They provide structures for students to be active decision-makers and self-advocates in a supportive and joyful environment.”

My daughter attended Sidwell from the seventh through 12th grades. She liked the school and did well. I thought some of the teachers were terrific. But there was no sign that the level of grade anxiety was any lower, or the level of joy any higher, than at hundreds of public high schools catering to affluent families that I have studied in the past two decades.

Information on college-level courses and tests is important because many high schools are run by people who do not believe average students belong in AP or IB. I can cite a long list of distinguished educators — Erin McVadon Albright, Mel Riddile, Jaime Escalante, Mike Riley, Doris Jackson and many more — who have proved the opposite. We should be able to see which schools come up short on this measure.

And why not identify and celebrate those who understand the power of rigor and depth for average kids? On the top of my private school list is St. Anselm’s Abbey, a small Catholic school in Northeast Washington that probably has a higher Challenge Index rating than any private school in the country.

This is the work of the school’s former headmaster, now president, the Rev. Peter Weigand. He told me when I started the list that he would be happy to supply the AP data because it was one of his school’s great strengths. He said that he doesn’t think my list is a measure of overall school quality but that it helps students and parents understand what is going on.

It’s a shame more private schools aren’t willing to let a little sunshine into their data banks and back up their claims that they are changing lives.