Nearly all of us are experts about something — Yorkshire terriers, Redskins quarterbacks, California native plants, whatever. Even obscure subjects have fans.

My obsession is the Advanced Placement program, those college-level courses and tests for high school students. I have studied AP for 30 years. I am saddened, as all devotees are, by outbursts of misinformation about my topic. The most recent example is an essay on by former AP government and politics teacher John Tierney, entitled “AP Classes Are a Scam.”

Without a shred of credible evidence — no data, no examples, no research — Tierney argues: “AP courses are not, in fact, remotely equivalent to the college-level courses they are said to approximate.” He seems unaware that AP classes and exams are designed by college professors to mimic their introductory courses, and that more than 5,000 college faculty have checked AP syllabi or graded AP exams to ensure it. Almost all colleges give credit or access to higher courses for good scores on AP exams.

At age 52, I took the AP U.S. history exam, and I just barely survived. I have spent hundreds of hours watching other AP classes and reviewing their exams. The courses are at least as rigorous as the introductory government and economics courses I took at Harvard.

“Two thirds of the students taking my [AP] class each year did not belong there,” Tierney says. “And they dragged down the course for the students who did.” I can’t judge Tierney’s teaching skills, but the successful AP teachers I have written books about say such statements often come from teachers who don’t understand how much they can help their students. The best educators find ways to raise the level of everyone in AP. They save kids from the limp courses that are often the only alternative to AP in high school.

Tierney should visit Fairfax County, which in 1998 adopted the AP-for-anybody policy he dislikes. The number of AP tests in Fairfax jumped from 10,234 in 1997 to 40,570 in 2011, a nearly fourfold increase. Those teachers proved that those new students did belong in AP. The number of students passing the exams increased 200 percent in that period, while the number of students in the system increased only 30 percent.

Tierney says “large percentages of minority students are essentially left out of the AP game.” The facts say otherwise. The number of black students earning 5s on AP tests — the top score — went from 796 in 1992 to 6,865 in 2012. The number of Hispanics getting top marks in that period went from 8,110 to 41,715. Black and Hispanic AP participation went from 11 to 23 percent of all test takers.

Much research shows students who do well on AP tests do better in college, but Tierney shrugs this off as “the same as saying that students who do best in high school will do better in college.” The research contradicts him. In a large Texas study, average students who got as low as a 2 on the AP test did better in college than similarly mediocre students who didn’t take AP courses.

A new study by the Center for Public Education goes further. It found that low-income, low-achieving students who took at least one AP course were 17 percent more likely to return for a second year of college than low-income, low-achieving students who didn’t take any AP courses.

Tierney suggests that the College Board charges too much for AP tests. I suspect many people feel the same way about tuition at Boston College, where Tierney worked for many years. But that has little to do with the quality of learning in AP or at BC.

There is much wrong with high schools today. It wastes time to take shots at college-level courses that are, I have learned from long study, the most beneficial challenges ever offered to American teenagers. If Tierney has something better, he should make it his favorite topic.