Students pray before class begins at St. Anselm's Abbey School in Washington, D.C. on April 14, 2016. The school is the top-ranked high school in the D.C. region on the America’s Most Challenging High Schools list for 2017. (Linda Davidson/The Washington Post)

This is the 30th anniversary of a moment that changed my life, when I discovered that a public school in a poor Hispanic neighborhood could produce 26 percent of all the successful Mexican American Advanced Placement calculus students in the country by giving students more time and encouragement to learn.

My focus since then has been to explore how this was done and identify those schools working hardest to challenge students from all backgrounds with courses such as AP and International Baccalaureate. One way has been to produce each year The Washington Post’s list of America’s Most Challenging High Schools. The 2017 edition has just launched.

The list shows a sustained increase in the number of schools that qualify through AP, IB and Cambridge test participation, even though the vast majority of U.S. schools still do not make the list. In 1998, the first year of what I call the Challenge Index, only about one percent of U.S. schools qualified. The number this year is up to about 12 percent.

The College Board has done much to get into AP more impoverished students like the ones I encountered at Garfield High School in East Los Angeles in the 1980s, even though thoughtless bipartisan congressional funding cuts have recently threatened that work. The latest data show how powerful was the inspiration from Garfield math teachers Jaime Escalante and Ben Jimenez 30 years ago.

America’s Most Challenging High Schools 2017

In 2003, 94,539 students from low-income families took an AP exam. By 2016 that number had jumped to 554,584, a 487 percent increase. The quality of the instruction has held up, refuting those who doubted Garfield could have produced a quarter of all the Mexican Americans passing AP Calculus tests in 1987. Many people at the time told me Garfield must have recruited some middle-class kids. They said children brought up in low-income environments lacked the conceptual math abilities of suburban kids, even though many Garfield AP graduates went on to become engineers and financial analysts.

Trevor Packer, the College Board vice president who runs the AP program, noted the average score on all AP exams has held steady from 2003 to 2016 despite the portion of low-income test-takers increasing from 9.5 to 21.8 percent. The average score was actually higher in 2016 than in some years when fewer students took AP, he said.

AP courses mimic introductory college courses in state universities. The final exams are written and graded by outside experts and thus are immune to the tendency in high schools to go easy on students who might complain, along with their parents, if they didn’t.

Nat Malkus, a research fellow at the Washington-based American Enterprise Institute, looked at National Assessment of Educational Progress math tests in 2000, 2005 and 2009 and found no sign that the achievement of graduates with AP course credit had been watered down. Teachers have shown what can be accomplished by encouraging every child to try at least one challenging course and giving each more time to learn through after-school and summer instruction.

That explains what has been happening with AP and IB instruction in the Washington area. Twenty years ago, Fairfax County was the first large district in the country to open AP and IB courses to all students who wished to participate, followed by most other districts in the region and several far away. More than 70 percent of Washington area high schools this year qualified for The Post’s list, six times the national rate.

The growth of AP and IB participation has also been fueled by selective college admissions offices using that as a measure of a student’s readiness for higher education. Many impoverished students have thrived in this atmosphere. The IDEA Public Schools network, with nearly 30,000 mostly low-income students in Texas, requires that each take 11 AP courses. Parents applaud their children breaking out of the remedial courses, with homework increasing gradually so they can get used to the load.

Several other programs are moving in that direction. The Jack Kent Cooke Foundation has made a $1 million grant to Bridge to Enter Advanced Mathematics (BEAM) so the New York-based program, which sharply accelerates math instruction for low-income students, can expand nationally. The National Math and Science Initiative has spent more than $200 million encouraging schools to add AP courses and motivate students to pass them, while training more teachers.

More such efforts will be necessary after Congress last year passed severe cuts in funds to pay for low-income students to take AP and IB tests. Those fees are as high as $93 for AP and $106 for IB because of the grading by experts. The federal neglect of such students appears to be the result of widespread ignorance on Capitol Hill of what is happening in high schools. Thirty-seven states have moved to fill the gap, Packer said, but 13, including Maryland and Virginia, have not. Low-income student AP participation increased this year in Maryland but declined in Virginia, and most states are uncertain what they will do next year.

Even students who do not pass AP exams appear to benefit from struggling in high school with the long reading lists and exams demanded of them in college. A study of 302,969 Texas high school graduates from 1998 to 2002 found that students with low SAT scores who had gotten a score of 2 on an AP test, below the passing mark of 3 on the five-point scale, had significantly better college outcomes than students with similarly low SAT scores who did not take AP.

Public high schools in the top 100 of The Post’s 2017 list include many with much poverty but AP and IB test participation rates higher than found in expensive private schools. The IDEA Mission College Prep school in Mission, Tex, had 91 percent of its students from low-income families. The Irma Lerma Rangel Young Women’s Leadership School in Dallas was 73 percent low-income. Preuss charter school at the University of California-San Diego was 100 percent low-income.

What I saw in East Los Angeles 30 years ago seemed clear to me. Dedicated teachers saw hidden potential in students who had not had much support. They convinced the teenagers they could do as well on college-level tests as kids in rich Los Angeles neighborhoods like Beverly Hills and San Marino. The teachers gave them the time they needed to learn, leading to changes in American high school education that no one, including me, ever anticipated.