The head of the union that represents teachers in DC Public Schools wants to change city laws to force teachers at the District's public charter schools to become union members.

Nathan Saunders, president of the Washington Teachers' Union, or WTU, said Wednesday that his members are concerned they will lose their union-negotiated contracts when DCPS closes some of its campuses next fall and teachers look to charter schools for jobs. The school system recommended Tuesday that 20 schools close at least temporarily and consolidate with other traditional neighborhood schools.

But the city's charter school chief says requiring these teachers to pay union dues and negotiate contracts outlining their hours and salaries would undermine the point of charter schools: flexibility to innovate in areas where the traditional schools have failed.

Charter schools in the District can unionize, whether as members of the WTU or by forming their own unions. None, however, has -- but Saunders said that's because the current charter school law is vague not because there isn't interest.

"Wages are a concern, benefits are a concern, and rights are a concern," he said.

For charter teachers to join the union, the D.C. Council likely would need to amend its books to say that charter school teachers are not exempt from the Comprehensive Merit Personnel Act. This would make WTU membership mandatory, as even those teachers who chose not to become full members would become "agency members," paying at least $60 a month in dues, and qualifying for some benefits and collective-bargaining rights. Full members -- as 64 percent of DCPS teachers are -- would pay at least $72 each month in dues and be entitled to legal representation, among other benefits.

D.C. Council Chairman Phil Mendelson was not available to comment Wednesday.

Congress also would have to approve any changes.

Scott Pearson, executive director of the DC Public Charter School Board, said he is not against charters electing to unionize, as some have done successfully in other states. But requiring charters to take this step is "ridiculous." Many of the District's charters have implemented extended school days, years or both.

"Charters outperform citywide averages on everything from proficiency rates in math and reading to graduation rates, and a lot of the reason they've been able to do that is we give them the freedom to run their schools without significant interference," Pearson said.

Still, some charter teachers said they would like to join the WTU. Scott Goldstein, a teacher at Next Step Public Charter School in Columbia Heights, said there was no opportunity for input from teachers when instructors received half of their expected raises last year.

"You're talking about scripting the hours and the salaries [with union membership]; you're not talking about scripting the curriculum," Goldstein said. "We'd still have the kind of flexibility we need."