San Francisco, struggling to recruit and retain teachers in a high-cost city, is foolhardy to walk away from a program that delivers a diverse group of 15 top-caliber recent college graduates to work in its most challenging low-income schools. It is especially regrettable to lose these teachers when they were ready to serve in some of the hardest-to-fill positions: science, math, special education and bilingual education.

“I respect the board’s authority to make these decisions,” Superintendent Richard Carranza said last month when forced to pull the annual Teach for America contract from consideration when it was clear it lacked the votes from San Francisco’s school board. “I just think it’s a missed opportunity for us to fill 15 classrooms (with) very scarce resources.”

Without question, the board had the authority to make the call — a very bad call, in our view.

For the past quarter century, Teach for America has served as a domestic version of the Peace Corps, leveraging federal and private funds to recruit and train college graduates to teach in the nation’s classrooms while they work toward their teaching credentials. The program provides support for the new teachers throughout their two-year stint. Local districts cover the teachers’ salaries and pay a modest fee to Teach for America.

Most important, districts who partner in the program are provided a ready supply of elite graduates at a time when the state is encountering an acute teacher shortage. San Francisco, of course, has the additional challenge of recruitment and retention in a city with celestial housing costs that are difficult to meet on even a veteran teacher’s salary.

Those who join Teach for America are particularly focused on working in low-income schools. Two-thirds of the TFA teachers in last year’s class were identified as people of color, compared with 29 percent of all new teachers in California — and 48 percent are the first in their family to attend college.

So who would object to this program?

Teacher unions, quite vociferously.

One of their objections is that programs such as Teach for America are no substitute for a more robust and sustainable commitment to bring qualified teachers into the neediest schools. They also worry that cheaper young teachers might displace higher-paid veteran teachers — though that certainly is not the case in San Francisco, which is scrambling to fill 500 slots by the start of school. Another big issue with the unions is the support TFA receives from advocates of vouchers and expanded charter schools.

In other words, it’s not part of the education establishment, and that can feel threatening to the defenders of the status quo.

“The status quo for schools is not OK. ... It needs to be interrupted,” said Lena Van Haren, principal at San Francisco’s Everett Middle School, who entered the profession through Teach for America. She credits the program for producing “one of the strongest pipelines” of diversity and bilingual teachers. She added that it “matches the vision for our school” of defying the dynamic of an educational establishment that was set up for “the dominant culture to thrive.”

Said Van Haren: “The way the decision was made did not feel very respectful of the professionals that are on the ground — the teachers and the principals.”

Beatrice Viramontes, Bay Area director for Teach for America, expressed disappointment that the school board members did not “meaningfully engage with data” or otherwise show much interest in visiting classrooms or hearing about the TFA participants who were volunteering to coach sports teams or serve as advisers to student clubs. She noted that 90 percent of the TFA-recruited teachers return for a second year, compared with 56 percent of other new teachers in the San Francisco district.

In short: The school board caved to the union.

Board member Rachel Norton acknowledged that “fierce opposition” to the program — mostly from the union — led her to withdraw her support for Teach for America. She said TFA’s training program “is good, it’s solid, it’s research based.” But she added that TFA was not necessarily better or worse than other new-teacher initiatives and that it simply was not worth another “serious, knock-down fight over 15 teachers” in a district with about 4,000.

Some of the classrooms that would have been filled by a TFA recruit might not have a full-time teacher in the fall.

“Yeah, it’s possible,” Norton said. “I hope it doesn’t happen.”

If it does, blame the school board. Teach for America clearly wanted to maintain a presence in San Francisco, but there is no shortage of other districts that will be eager to scoop up the 15 recruits. “We can’t meet the demand across the Bay Area,” Viramontes said.

This is San Francisco’s loss.