Washington Teachers’ Union President Nathan Saunders said Wednesday that he wants to unionize the city’s charter schools and will push for legislative changes to make it easier to organize their teachers, who educate a growing number of D.C. students.

The move comes in response to Chancellor Kaya Henderson’s proposal to close 20 traditional public schools across the city.

“It was commonly conceived by our members that many of these schools might receive pressure to reopen as charters,” Saunders said, “and they wanted to look at options for union membership should that happen.”

There are some unionized charter schools across the country, but no D.C. charters have been organized.

Saunders said that he has the legal right to organize charter schools but that it is difficult because they are exempt from the law that requires the city to enter into collective bargaining with public employees.

The teachers union is “prepared to dedicate significant resources” to ending that exemption, Saunders said, bringing charter schools under the same labor law that governs the city’s public schools.

That would require approval from the D.C. Council and Congress, which seems politically unlikely given a Republican-led House with little interest in helping teachers unions grow and strong bipartisan support for charter schools.

“I don’t see how it could be a worse idea, and it’s not going anyplace because the Congress will never approve it,” said Robert Cane, executive director of the pro-charter Friends of Choice in Urban Schools.

The freedom to employ non-unionized teachers is part of what sets the charter movement apart from the traditional school system, Cane said.

“We have these two reforms working side by side, and the unionized teacher idea is part of the other reform — the DCPS reform — and it has no place in the charter schools,” he said.

Charter schools enroll more than 40 percent of the city’s students, a proportion that could increase under Henderson’s proposal. Charter teachers are often paid less and have fewer protections than teachers in traditional schools, Saunders said.

“Many teachers have complained to us and have asked us to organize them so they could achieve better working conditions,” he added.