Development plans are emerging for the site of a long-vacant Harlem school building, but the proposal is generating strong opposition among neighborhood groups who question whether more than 100 co-op apartments would be affordable to local residents.

The building that formerly housed P.S. 186 at 145th Street between Broadway and Amsterdam Avenue, is owned by the M.L Wilson Boys and Girls Club, which bought it from the city in 1986 for $215,000. Though their agreement with the city called for development to be mostly completed within three years, the site has remained vacant more than twenty. ARCTAC Development Partners, selected by the club to develop the site, presented a plan to the Community Board 9 in June that consists of two towers that would include a facility for the Boys and Girls Club, space for stores or nonprofit organizations, perhaps a post office, and 101 co-op units. Twenty-five percent of the units would be market rate, and 75% would be affordable for families earning up to 175% of area median income. The Boys and Girls Club would serve as the landlord for the new development, and would likely generate millions.

“It stood up above all the rest,” the chairwoman of the board of the Boys and Girls Club, Shirley Lewis, said of ARCTAC’s plan, which was chosen from six that were submitted last year.

For the plan to go forward, the city would have to lift a restrictive deed that requires 85% of the site be dedicated to non-profit uses, and that requires approval by Mayor Bloomberg and the president of Manhattan, Scott Stringer.

The director of land use for Mr. Stringer, Anthony Borelli, said that if the plan could be refined to meet the needs of the community, the office would consider modifying the deed. A representative of the mayor’s office dealing with the development did not return phone messages.

Some community groups say that though the apartments are touted as “affordable” housing, they would be out of reach for most Harlem residents. The area median income — which is calculated based on all of New York City and some of its suburbs — is $70,900 for a family of four. That would mean that the “affordable” co-ops would be targeted at families making up to $124,075. The median income in Community District 9, where the site is located, is about $30,000.

“That’s not affordable,” said the executive director of Broadway Housing Communities, Ellen Baxter, “That’s just rhetoric.”

In an effort to prevent the proposal, another neighborhood group, Brotherhood/Sister Sol, has gathered 5,000 signatures on a petition demanding that the deed restriction be kept in place.

A member of the development team at ARCTAC, Tom Ciano, said the developer would try to bring the cost of the apartments down as much as is economically feasible.

“We’re trying to reach as low as possible,” he said, adding that he would like to see some of the units be affordable to families making about $56,000 to $70,000.