Now Mr. Cortines plans to send specialists to the 40 failing schools once a week, retrain the teachers and even replace principals if necessary.

But he said he would not apologize for making decisions in troubled districts - including suspending school board members and replacing principals - without their input.

Many academy graduates, he said, were placed in tough schools, replacing poor principals that he described as "place-holders."

His actions could include replacing principals, changing curriculums and creating several smaller schools within a large school.

They include replacing principals, rearranging the teaching staff, adding prekindergarten or after-school programs, dividing each school into smaller schools, and changing the curriculum.

Her proposal comes as an increasing number of schools in New York City and across the nation are struggling to replace principals who have retired or quit in the face of mounting job pressures.

"It isn't going to replace good teaching, good principals, small classrooms or anyone of dozens of things."

She replaced principals in about half the schools and set specific academic goals.

"I have no control over ethnic makeup," said Dr. Copes, who has already replaced several principals and made other changes.

Mr. Singer recently criticized the city school system for the lack of progress in replacing the principals and assistant principals who took the early retirement offer last summer.