An International Baccalaureate student in Fairfax County, Va., shown in a file photo. (Dominic Bracco II/The Washington Post)

One of the most unusual courses in high school these days is TOK, the initialism for Theory of Knowledge, part of the International Baccalaureate program. Most Americans have never heard of it.

It is a course on critical thinking and how we know what we claim to know. It demands a lot of writing and thus, by the standard teenager definition, is not easy. But most of the IB teachers I have encountered, and many of their students, call it special and deep, a distinctive element of a program now offered in nearly 900 U.S. high schools.

Jeremy Noonan felt that way when he was a science teacher in Douglas County, Ga. He taught Theory of Knowledge for four years, with increasingly good results.

But his is a story of TOK going wrong, something I had not encountered before. When many students began to complain that it was too difficult, Noonan said his principal asked him to make it easier. Noonan said he learned later this was so that enrollment in IB — a major selling point for the school — would not decline.

Douglas County school officials declined to comment on Noonan’s account.

IB’s own data show that only 0.5 percent of students get a failing TOK grade. Grades on the TOK and IB’s unusual 4,000-word extended essay earn a maximum 3 points toward an IB diploma, while each of the six required subject grades earn up to 7 points.

Spencer Caro, a former student who said Noonan’s TOK was the “the highlight of my IB experience,” noted that “students only need a D in TOK” to qualify for the IB diploma, and consequently many don’t try very hard.

Even a sophisticated course such as TOK can be damaged if a school does not guard against softening demands. Noonan said he did not expect TOK to take much time outside of class compared with the main IB courses, but to “get an A in the course, students had to be making progress and perform at an excellent level.”

It took time to establish that mind-set. Noonan said many of his first TOK students were in a state of revolt against the IB program. They thought they didn’t need it to get into a regional public college with low admission standards. But as they began to see how intriguing TOK was, attitudes improved and essay scores rose above global averages. “Parents regularly told me that they saw their children maturing into adult thinkers before their eyes,” Noonan said. “Alumni described the advantages they had in college due to being able to argue well and think from different points of view.”

When he resisted diluting the course, Noonan said, he was reassigned in 2015 to non-IB science courses. His replacement in Theory of Knowledge, according to Noonan, had no IB teaching experience. Noonan said some students told him that TOK had become “the course where you go to catch up on work from your other classes.”

Noonan had assigned several graded essays each year. He said the new teacher assigned none. Noonan said his principal told him that at a regional meeting of IB principals, it was agreed that TOK should be easy and not treated as a serious course.

That was not what Dina Dreyfus, inspector general of philosophy in the French government’s education department, had in mind when she introduced the TOK idea to the original plans for IB. The courses were formulated by European and American teachers at the International School of Geneva in the 1960s and 1970s.

Dreyfus, married at the time to legendary anthropologist Claude Levi-Strauss, was a tough educator who fought for her idea. Such enlightened stubbornness is necessary when defending courses as complex and interesting as TOK.

I remember how the eyes of Bernadette “Bernie” Glaze, a stalwart of the early years of TOK classes in Fairfax County, would light up at the journals her students were writing and the connections they were making with the intellectual roots of civilization. Glaze died much too young, in 2008 at age 62, but there are still plenty of teachers like her enshrining TOK in student memories. Turning it into a Mickey Mouse course is not the best way to teach our kids how to understand the world.