The Zoning Board of Appeal today approved plans by the Neighborhood House Charter School to add a gym and 12 new classrooms to handle 70 eighth-grade students at its Queen Street campus - but with a proviso that the school not be allowed to educate more than 525 total students at the site.

The vote on the 21,000-square-foot project came after neighbors said the expansion would exacerbate traffic problems in the neighborhood and violate an earlier memorandum of understanding they said had limited enrollment at the site to just 400 students.

School officials said their plan would help traffic in the area, by increasing the number of cars that could queue on the campus in the morning and afternoon without spilling onto nearby streets and denied they had signed an agreement in 2003 to limit enrollment to 400 students, only that they had noted that, at the time, the school had 400 students.

The board voted unanimously to grant the school waivers from the lot's density, height and front-yard zoning requirements. In addition to capping the school's enrollment at the site - Neighborhood House has a separate high-school building elsewhere - the board also required it to work with neighbors on the use of trees and shrubs to provide a buffer.

School officials told the board that in addition to moving eighth graders from the high school to Queen Street, the gym would give students a place to get some exercise in winter months and allow for performances and interscholastic sports. They said they had agreed not to rent the gym to outside parties and that it would be closed completely on weekends.

Brad Watkins, who lives at 9 Queen St., right next to the school, told the board he would appeal its decision, which would mean a lawsuit in Suffolk Superior Court, for several reasons, including what he said was the school presenting different plans to the zoning board than residents were shown, that the increase in density is just too much and that the school refused to buy additional land on which to build new classrooms.

"It's way out of touch with the original variance," he said.

Some residents supported the proposal. "Yes there is traffic, but we live in a city," one resident said.

The mayor's office and City Councilor Frank Baker (Dorchester) supported the proposal. Both acknowledged traffic problems in the neighborhood, but said they were "regional" in scope and that it would be unfair to blame the school for them. Baker said 60% of the school's students live in Dorchester and said the city has committed to working on the traffic issues.

City Councilor Althea Garrison (at large), opposed the project. An aide told the board the proposal would make neighborhood traffic problems worse, "in a dense urban neighborhood whose streets were never intended for [daily school transportation]," that it failed to recognize the site's historic nature as a former dormitory and that the proposal would violate state law.

Neighborhood House small-project review application (4.8M PDF).