Former publishing executive Cathie Black's lack of education experience made her a lightning rod for critics.

New York City Mayor Michael Bloomberg said former publishing executive Cathie Black was the perfect choice to head the city’s 1.1 million-student school system, because she was “a superstar manager.”

But her resignation April 7 after three contentious months on the job was the latest in a series of third-term setbacks for Bloomberg—and a defeat of his high-profile school reform bid to hire a business-minded outsider like himself to run the city’s schools.

“I will take full responsibility for the fact that this has not worked out as either of us had hoped or expected,” Bloomberg said at a hastily called City Hall news conference to announce Black’s resignation. She did not attend.

Bloomberg surprised even some officials within his administration when he plucked Black from the business world and installed her as head of the nation’s largest public school system. Critics, including many parents of public-school students, assailed her lack of experience as an educator. She had no background as an educator, had never attended public schools, and had not sent her own children to them.

On the job, Black failed to convince the critics they were wrong. Her few unscripted public appearances were marked by gaffes. Meeting with parents concerned about crowded schools, she joked that birth control was the solution. Faced with hecklers at a meeting about closing schools, she heckled back. Two polls put her approval rating at 17 percent.

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Teachers at some schools erupted in cheers when the news of Black’s resignation broke.

And now, Bloomberg has chosen a new schools chancellor who is Black’s opposite in many ways.

Deputy Mayor Dennis Walcott, 59, is a graduate of New York City public schools and hold’s master’s degrees in education and social work. A former kindergarten teacher, Walcott founded the Frederick Douglass Brother-to-Brother program, a mentoring program for boys.