The teachers we hear most about are larger than life — charismatic, aggressive, loud. Educators like Jaime Escalante, Rafe Esquith, Dave Levin, Mike Feinberg and Harriett Ball are impossible to ignore. But we overlook many teachers who use quiet persistence and soft words to change our schools for the better.

Take the case of Betsy Calhoon, who died of a heart attack June 11 at age 67 while vacationing in St. Croix in the U.S. Virgin Islands. A huge cohort of Fairfax County students, teachers and parents remember how much that slender, red-haired social-studies teacher accomplished with a combination of gentle manner and iron will.

Calhoon transformed a troubled school, Mount Vernon High, and became a model for persuading reluctant students to embrace academic challenges. She not only changed her school, but also showed one of the nation’s largest school systems how to involve the children of minority and low-income families in the most demanding courses available in U.S. high schools.

Yet in 1993, when she became the coordinator (nobody else wanted the job) of one of the first International Baccalaureate programs in Fairfax, her prospects were bleak. Advanced Placement was the ruling college-level program in the county. Few people embraced the change to IB, or the idea of opening it up to students who had previously not been asked to deal with difficult school assignments.

Mount Vernon’s only physics teacher — a bright young man who was wonderful with kids — did not like IB’s more experimental, hands-on approach to his subject. He left for another school. The foreign-language teachers were uncomfortable with the new curriculum. Calhoon’s own department, social studies, was in an uproar because for the teachers who had agreed to do IB, their jobs were protected, while others had to leave because enrollment was down and there were no slots for them.

The first IB exams brought more bad news. The average physics score was only 3.5, below the international average of 4.39. The biology average was 3.69, also below standard. The student body president blamed his failure to get into an Ivy League college on IB. He said he would have gotten better grades in the old courses.

Calhoon loved Mount Vernon’s ethnic diversity. Forty percent of the students were minorities. Her husband, Chuck, was an officer in the Marines, one of the most integrated institutions in the country. They were raising their two children, Mary Elizabeth and Thomas, to respect people of all backgrounds. But despite her efforts to involve all students in IB, barely 10 percent of the participants that first year were Hispanic or black.

She stuck with it. She recruited teachers who liked the IB approach. She amazed county school leaders by persuading Bernie Glaze, chairman of the social-studies department at the nationally known Thomas Jefferson High School for Science and Technology, to take a pay cut and transfer to Mount Vernon.

Teaming up with many other talented teachers and administrators, Calhoon and Glaze eventually turned the school around. They were both the oldest children in their big families, with good marriages and a determination to raise the performance of kids from low-income families. Glaze later took charge of all IB and AP programs in Fairfax. Like Calhoon, she died too young, of cancer in 2008 at age 62.

In 2003, Calhoon and her husband retired and moved to Beaufort, S.C. She got involved with IB programs there. She left behind at Mount Vernon one of the strongest college-level programs in the country, with improved scores and 35 percent of the participants from black or Hispanic families.

Some of those students told me that they would have quit the annoyingly difficult IB program except for Calhoon, who never tired of telling them, in that soft voice, that they had great potential, so why waste it?