NEW YORK -- Schools Chancellor Cathie Black resigned Thursday after a rocky three months that included parents heckling her at board meetings, plummeting poll numbers and the departures of several deputy chancellors.

Black and Mayor Michael Bloomberg met Thursday morning and "mutually agreed that it is in the city's best interest if she steps down as chancellor," Bloomberg said.

"We both agreed that the story had become her and it should be about the students," the mayor said at a City Hall news conference. Black did not attend.

The mayor appointed Deputy Mayor Dennis Walcott as the new schools chancellor.

The mayor's appointment of the former Hearst Magazines chairwoman has proven to be one of the deepest embarrassments of his administration.

Black had no previous experience in education, and her appointment was a surprise even to some officials within the administration. There was no formal search announced.

When faced by heckling from hostile parents at one community meeting, she heckled them back. And she joked that school overcrowding could be fixed with birth control.

A Marist College/NY1 poll released this week found that 17 percent of New York City adults approved of the job she was doing, down from 21 percent in early February.

Several department officials left after Black became chancellor in January, including the resignation this week of deputy schools chancellor John White to head a school district in New Orleans.

"I will take full responsibility for the fact that this has not worked out as either of us had hoped or expected," said the mayor, known as a fierce defender of his administration's top appointments.

With no credentials as an educator, Black needed the waiver from state education Commissioner David Steiner, and an advisory panel recommended that he deny it. But Steiner indicated he would give the green light if

Bloomberg elevated a deputy chancellor with an education background.

The mayor eventually agreed to create the position of chief academic officer as a no. 2 to Black.