While the chances of Columbia University faculty members getting their children into the university’s elite primary school have diminished sharply, university officials have taken steps to ensure vacancies for the families of newly recruited scholars.

In a letter sent out November 12, Provost Alan Brinkley informed faculty members and other Columbia employees that “a small number of slots will be reserved each year for children of newly-hired officers of instruction.”

Other faculty members and university employees wishing to enroll their children are required to participate in a lottery process that determines selection. In the latest admissions round determining placement for next year, the school rejected twice as many children as it accepted among families affiliated with Columbia, according to officials.

Columbia had originally intended the School at Columbia University as a recruitment tool to lure top-flight scholars and their families to Morningside Heights. By assuring slots for new recruits, Columbia in a way is protecting its investment and preserving the school’s recruitment function.

The policy, however, is likely to become a target of criticism from faculty members whose children have been rejected. As was negotiated between Columbia and Community Board 7, the school is divided roughly equally between students from families affiliated with Columbia and students from community school districts 3 and 5. The school district children also are selected by a lottery.

Founded in the fall of 2003, the school is adding a seventh grade, pushing the student population to more than 400 students. The school occupies the first five stories of a 12-story building on 110th Street and Broadway.

Columbia officials have had to tighten admissions polices as the number of parents seeking to enroll their children has shot up. In previous admissions cycles, the children of faculty members were all but guaranteed admission into what is perceived as one of the top primary schools in the city.

Some of the new policies addressed in Mr. Brinkley’s letter have infuriated a number of parents. In the change that has sparked the most outcry, Columbia no longer gives special preference to siblings of students already admitted. A number of parents who assumed their children would be attending the school have been forced to place their children elsewhere.

Mr. Brinkley stated in his letter that admission preference will be given to faculty members over administrative employees. The faculty members whose children are accepted will be evenly distributed between Columbia’s different academic schools.