The District school board voted unanimously last night to begin negotiations with Carl A. Cohn to become the city's next schools chief.

The board's action came without discussion of the terms that Cohn this week attached to accepting the job, including that he would serve only a year.

School board members said the process of selecting Cohn, who was superintendent of schools in Long Beach, Calif., for a decade, was cause for celebration. "I would love to have Dr. Cohn be the leader of our school system," said school board member Julie Mikuta (District 1).

However, several board members, who had hoped to find a permanent superintendent, said in interviews that they were concerned that Cohn would not sign a longer contract. Some said they hoped to change his mind.

The school board's vote came a day after an education collaborative of seven city and school officials recommended Cohn to the board, which will make the final decision on who should lead the 64,200-student school system.

Yesterday, District Mayor Anthony A. Williams (D) said that he wanted Cohn to become the city's next superintendent even though he would not agree to a long-term contract. Williams said that in a year, Cohn could put in place "the building blocks to rebuild the system" and use his stature in the education field to "bring in a good successor over the long term."

Some parent leaders reacted with dismay to Cohn's comments that he did not want to stay longer than a year. They said that the school system needs stability and that such a short tenure would not be enough time to fix its many problems.

"It's like having the air let out of your balloon," said Darlene Allen, head of the city's Congress of PTAs and a member of a superintendent search committee that screened candidates. "He is a quality candidate, but we need someone who is going to at least be willing to commit for longer. . . . A year I don't believe is going to be enough time, and it's going to take us backwards, and we need to move forward."

Cohn said in an interview Tuesday that even before he will agree to come to the District for a year, city officials need to hold a "summit" with congressional leaders and commit to making a number of changes in the way schools are overseen. One of those changes, he said, is to have the school system's chief financial officer report to the superintendent and not to the city's chief financial officer. He also said that the school system's fiscal year should be adjusted to match the school calendar and that school contracts worth more than $100,000 should not be subject to council approval.

Cohn, who did not return a phone call yesterday, said Tuesday that accepting a permanent post would not be "a prudent risk." He also cited family reasons. Cohn said that during a one-year term as superintendent, he would bring in a "turnaround team" and put in place "central pillars of support that are needed for teachers and principals."

Williams said yesterday that he plans to work with government leaders to convene the kind of summit that Cohn wanted. Williams said that he wanted to create the best environment for a superintendent to succeed. "I'm looking to him for guidance," the mayor said.

Williams's first choice for superintendent, former New York City schools chancellor Rudolph F. Crew, took the top schools job in Miami last month. The D.C. superintendent's job has been vacant since November, when Paul L. Vance quit.

The search got off to a slow start, and in the meantime, the city's first interim superintendent, Elfreda W. Massie, quit to take a job in the private sector. The system is being run by a second interim superintendent, Robert C. Rice, who was acting chief academic officer.

Several school board members said that Cohn, a schools consultant and professor at the University of Southern California, was the best candidate for the job.

Board member Carrie L. Thornhill, a mayoral appointee, said she would be willing to consider a one-year arrangement. "I think he can accomplish a number of things in a year, including building a case for him to stay longer," she said.

Board member William Lockridge (District 4) said he had not decided whether a one-year contract is acceptable. "We've had no stability at the top," he said. "I'm concerned about that. I'd have to hear more details about . . . what he would do for a year."

Several education leaders who are familiar with Cohn's work said the District should hire him, even for a short time. They said that a one-year appointment would allow Cohn to push through difficult reforms that a permanent superintendent might be afraid to make.

"It's usually done in circumstances where . . . somebody needs to come in for a short period of time to do that heavy lifting in a way that a permanent superintendent couldn't come in and do and survive," said Michael Casserly, executive director of the Council of the Great City Schools, a coalition of 61 urban districts. "These kinds of reforms often break enough china that a permanent superintendent might not be able to survive it politically over a longer period."

Casserly, who has been trying to persuade Cohn to take the D.C. job, said it would be best if Cohn stayed more than a year. But Casserly said a one-year term is reasonable.

And given that there is no other candidate who has attracted widespread support, he said, "a year under this circumstance is better than a year of nothing else happening."

Analysts said short-term superintendents have been effective in making difficult changes in some cities, including Los Angeles, where Ramon C. Cortines, a former New York City schools chancellor, served as interim superintendent for eight months in 1999 and 2000.

Staff writer Lori Montgomery contributed to this report.

Carl A. Cohn, a consultant and University of Southern California professor, said he would consider a year-long appointment to help reform the District school system.

Mayor Anthony A. Williams at an earlier briefing. He said he believes "it's better for our system to have him come in here, even if it's only for a year, and begin putting in place the building blocks to rebuild the system."