Children from Oyster Adams Elementary walk to their school. A new policy aims at giving parents more choices to enroll students in charter schools within walking distance of their homes. (Kate Patterson for The Washington Post) (Kate Patterson/For The Washington Post)

Thousands of D.C. children who live near public elementary charter schools could soon qualify for a new admission preference to help them enroll in those schools under a plan Mayor Muriel E. Bowser (D) announced Monday.

Under the city’s current policy, students have a guaranteed seat in a traditional public school near their home. But those assigned neighborhood schools — all part of the D.C. Public Schools — are sometimes more than a half mile away. That can make it hard for elementary students to walk to school.

In those cases, Bowser said, families that live no more than a half mile from a charter school should get special consideration through the city’s school lottery system. The mayor said she wants to “make it easier for more of our students to enroll in charter schools that are within walking distance of their home.”

Bowser’s proposal for a “walkability preference” would target an estimated 10,000 students who live more than a half mile away from their assigned traditional school but less than a half mile from a charter school. Charter schools would not be required to offer an admission preference to those students, but they would be allowed to do so.

The policy, if approved by the D.C. Council, would take effect in the 2018-19 school year. It could have a significant effect on a public education marketplace that gives parents many options. About 29,000 students from pre-kindergarten through 5th grade were enrolled in D.C. Public Schools in 2015-16, compared to about 21,600 in charter elementary schools that year.

Bowser has pushed to increase school choice in the District. But some education advocates questioned Monday’s proposal. They said it could drain students from traditional D.C. schools and make it harder for students from low-income families to get into top charter schools, which are often located outside of their neighborhoods.

In 2012, a 12-member D.C. task force considered whether to require all charter schools to offer a neighborhood preference, but the idea was rejected.

Council member David Grosso (I-At Large), who chairs the Council’s education committee, said he has some “reservations” about the proposal and has already heard some “vocal uproar.”

“This is very complicated stuff that could perpetuate divisions within our city and communities, and it will have to be very thought through,” Grosso said. “I am not too inclined to support it, but I am open to having a conversation.”

Under the lottery system, there are charter school enrollment preferences for children of founding board members and siblings of current students. Grosso said adding another preference would possibly deny students an equal opportunity to enroll in quality schools.

It is unknown how many of the District’s 82 elementary charter schools support the measure. Scott Pearson, executive director of the D.C. Public Charter School Board, called the measure an “interesting enrollment proposal that addresses real issues families face.”

He added, “All preferences have complex effects so we’re speaking with school leaders and others to better understand their perspectives.”

Eboni-Rose Thompson, the chair of the Ward 7 education council, said she fears the changes would mean less access to high-quality schools. In Ward 7, for example, there are no dual-language charter schools. Most of those schools are in Wards 1 and 4. Under the proposal, some students in Ward 1 might have greater access to those schools because they live near them. That would leave fewer seats available for students from Ward 7.

“When we accepted charters into the city, they were supposed to be city-wide schools. What happened to that?” Thompson asked. “Do we just throw that away because we are trying to get at a different problem?”

Caryn Ernst, a parent activist, sits on a mayoral task force that aims to increase collaboration between charters and the school system. Ernst said she was surprised to learn about Bowser’s proposal. The task force last fall considered and rejected a similar idea, according to Ernst.

“The idea that she would announce this is astonishing to me and it completely undermines the purpose of a task force,” Ernst said.

Bowser also proposed raising annual facilities funding for charter schools, to $3,193 per pupil. That would be 2.2 percent more than the current level of $3,124 per pupil.

Bowser announced her proposals at D.C. Bilingual Public Charter School in Northeast Washington, along Pearson and Deputy Mayor for Education Jennifer C. Niles. John Davis, the interim chancellor of D.C. Public Schools, was not present.

Antwan Wilson, the incoming chancellor of DCPS, starts his new job Wednesday.

Michelle Lerner, the spokeswoman for DCPS, said the school system looks forward to working with the city on the lottery changes “so that all families can access high-quality schools.”