Immigrant families who want to send their children to some of the Upper West Side’s best schools appear to have won concessions from the Board of Education stemming from a public campaign they launched two years ago.

The schools chancellor, Joel Klein, agreed this week to create a new lottery system, the first program of its kind in the city, for hundreds of empty public elementary school seats in District 3, which runs from 57th Street to 122nd Street. Because parents who send their children to private or parochial schools, the district has an unusually high number of spots available each year, but they are often out of reach for immigrant families who are unaware of the openings. Charging that the unequal racial distribution in the district amounts to segregation, the Center for Immigrant Families threatened legal action two years ago.

Currently, principals have the discretion to admit students outside of their geographical zone, a system that benefits savvy parents who understand the system. Under the new model, there will be one application for all the schools, and openings will be filled through a lottery process beginning with the 2006-07 school year. In addition, siblings will continue to have preference in applying to schools.

“The intention is to make the admissions process more fair and equitable,” the chancellor’s senior counselor on education policy, Michele Cahill, said. “We’re going to make it known that there are these kindergarten seats available throughout District 3.”

The Center for Immigrant Families celebrated yesterday what it considers a victory for the neighborhood’s disadvantaged children. “This is a historic moment providing an important example of the strength of a community coming together to fight for its rights,” an organizer of the group, Priscilla Gonzalez, said. The next step, she said, is to ensure that socioeconomic class is taken into consideration and to alter the gifted and talented programs.

“The gifted and talented programs are creating segregated schools within schools,” she said. The group is still considering legal action with the Puerto Rican Legal Defense and Education Fund.

Critics charge that a lottery system may actually hurt some of the more diverse schools in the district. It will affect two of the most racially integrated schools in the district, Public Schools 75 and 87, said Clara Hemphill, director of Inside Schools, a project of Advocates for Children.

“I can’t think of a single school in the district in which the lottery system would increase racial integration,” Ms. Hemphill said. “There are so few racially integrated schools in the city, it seems a shame to upset the balance at those few schools.”

Instead, Ms. Hemphill said, the emphasis should be on improving the overall school system. “You want to give a fair shake to poor, immigrant parents, but the way to do that is to create more good schools and not to replace one arbitrary admissions system with another,” she said.

Council Member Gale Brewer, a Democrat from the Upper West Side, also questioned whether the policy would make the schools more diverse. “Right now, some of these schools do outreach beyond the immediate area. They try to work on diversity,” Ms. Brewer said. “I don’t know if you are biting your nose to spite yourself.”

Ms. Brewer also raised concerns about ensuring sibling preferences and the costs of administering the project, which will not include extra staff.