D.C. mayoral candidates faced a math problem of sorts Wednesday night at the campaign’s only major forum devoted to education: In 1966, the District had about 147,000 students in 196 schools. Now, there are 86,000 students in 213 neighborhood and charter school buildings, yet the city continues to open charter schools.

Is this path sustainable?

The three leading candidates differed on details, but there seemed to be a consensus on the need for more planning.

Charter schools are nearing parity with traditional schools — accounting for 44 percent of the public student enrollment and occupying about the same number of buildings — and the next mayor will have to manage a highly unusual hybrid system of city schools that compete for students and resources.

There is little coordination and few restrictions on where, what kind or how many schools open. That has frustrated some officials and parents, who worry about redundant spending and programs, and there are concerns that, without intervention, charter schools will overwhelm neighborhood schools.

The three candidates agreed Wednesday night that better coordination is a priority, though they had different ideas on how to accomplish it.

D.C. Council members Muriel E. Bowser (D-Ward 4) and David A. Catania (I-At Large) emphasized voluntary measures to encourage cooperation. Independent candidate Carol Schwartz went further, saying that, if necessary, she would pursue an amendment to the federal Education Reform Act to require coordination.

“I think we can ask Congress to tweak that bill,” Schwartz said.

The forum, at the Thurgood Marshall Center in Northwest, was organized by a coalition of education advocates and organizations that signed on to a list of principles they say would move the city closer to a goal of quality traditional public schools in every neighborhood.

It was a rare opportunity for voters to hear the mayoral candidates talk in detail about their visions for education. Bowser, who has declined most invitations to debate, made an appearance at the last minute.

The moderator, Natalie Hopkinson, opened the event by describing her experience as a parent in the District. Her family’s assigned elementary school was closed twice, she said, and the family spent five years on a waiting list for a charter school and has crisscrossed the city looking for good schools.

“We’ve tried parochial, charters, everywhere but our own neighborhood school,” she said.

The candidates had about 30 minutes each to repond to questions, and they filled out written surveys beforehand.

(The surveys are posted online at wapo.st/1024survey).

Catania said that as mayor, he would convene charter and traditional school leaders “from a place of trust.” He talked about bringing advocates together to push for better special education, which led to reform measures the D.C. Council passed this month.

“I don’t believe in putting an artificial hold on charters while [D.C. Public Schools] struggles to improve itself,” Catania said. “We need to put DCPS on equal footing, and DCPS needs to compete.”

Bowser said she would promote voluntary collaboration with the help of incentives, including surplus school buildings that charter schools are eager to lease. But she did not preclude resorting to a legal remedy. “I am willing to do whatever it takes to best leverage our public school dollar,” she said.

The conversation included the growing achievement gap, the high rate of teacher turnover and student mobility.

Schwartz touted her background as a former special education teacher and a public school parent. She reminded the audience that in 2007, she was one of two D.C. Council members who opposed the mayoral takeover of schools. “We are a city deprived of democracy,” she said.

To address the achievement gap, she proposed an “all-out call to service for retired educators” who would volunteer to tutor students individually.

Catania described his study of the school system, including nearly 150 school visits, since he became chairman of the council’s Education Committee. He cited legislation to curb social promotion and to increase funding of schools that serve students with the greatest needs.

Catania said that the country “went a little bonkers . . . with testing” and that tests should be more reflective of “additive,” or growth, measures, which evaluate how much students have learned during a school year instead of just determining whether they are working at grade level.

Bowser emphasized her commitment to keeping Schools Chancellor Kaya Henderson in her job. “The best way to protect the investments we have made — over $1 billion in seven years — is to have strong, consistent leaders at the top,” she said.

She said that the school system has succeeded in attracting families with children in the early grades and that it now needs to focus on middle schools. She said she would open four more neighborhood middle schools and work to improve extracurricular offerings and academic programs.

After the forum, Deborah Menkart, executive director of the nonprofit Teaching for Change, said she was dismayed that the candidates seem so focused on expanding choice, which she believes could undermine neighborhood schools. “It’s a runaway train,” she said.