An 11th-grader studies during an International Baccalaureate Spanish program at Annandale High School in 2008. (Dominic Bracco II/The Washington Post)

When I lived in Westchester County, N.Y., 20 years ago, I knew Dobbs Ferry High as a little school in a small town about six miles from my home. It had little to distinguish it.

Now I learn the three-story brick school on the Hudson River has undergone a startling transformation worthy of study across the country.

In 1998, a year after I left Westchester, Dobbs Ferry High started an International Baccalaureate program, with its strong emphasis on writing and its challenging five-hour final exams with almost no multiple-choice questions. But like most schools, Dobbs Ferry involved just a small number of students in IB. As veteran Dobbs Ferry teacher Marion Halberg put it, the program “didn’t address the needs of the school at large.”

Then the school made an extraordinary move. Assistant Principal Sandra Intrieri selected Halberg as the new IB coordinator, even though Halberg had never taught an IB class. Intrieri saw this as a way to get every student into IB. Halberg identified herself as “one of the teachers who would turn and stop paying attention when the program was discussed at faculty meetings.” She taught English for speakers of other languages.

In 2005, I wrote a book about IB in the United States and have continued to report on the program. I have never heard of a school appointing a non-IB teacher to coordinate an established IB program. Administrators rarely put neophytes in charge of complex existing initiatives.

Halberg and the district’s other IB reformers brought every student into the program, including those in special education. I can find only three other public neighborhood IB high schools that have done this in the United States. George C. Marshall High in Fairfax County plans to join that group next year.

Halberg described the results in two long posts on the IB Community Blog: “Today, every student in the 11th and 12th grades takes DP [Diploma Program] English and DP mathematics because that’s all we offer. In addition, most students take at least one other IB course but usually more, and approximately 25 percent of the graduating students each year are full diploma candidates.”

To earn an IB diploma, which comes in addition to the usual school diploma, a student must receive good grades on multiple assessments in six subjects and on a 4,000-word research paper. They must pass other IB courses, such as the celebrated Theory of Knowledge class, and do community service.

When Halberg took the training required of all IB teachers, she concluded that the program’s emphasis on writing and critical thinking would work for everyone. “All students deserve and should have equal access to what everyone else has,” she said.

The school sent all staff to IB training, including the counselors and special education teachers. Halberg said “teachers in ninth and 10th grades began to see what they were preparing their students for. . . . We have taken advantage of IB’s own evolution in terms of granting accommodations to those with special needs.”

It took time and effort to explain to parents why IB was in some ways better than Advanced Placement. Even if many students did not score high enough to earn IB diplomas, the improvement in their thinking and writing helped them in college and in life, as many Washington-area students have told me.

Lisa Brady, the district superintendent, said she spent many months meeting with groups of parents in their homes and telling them, “We simply cannot continue to sort kids based on our preconceived notions about their capabilities.” Principal John Falino said, “This has been a major focal point for us.”

Dobbs Ferry has just 440 students. Just 15 percent are low income. That might make it easier to enact such great changes, but most schools of that size haven’t even considered their hidden potential. This would be a good time to start.