Do public school teachers get tenure just by breathing?

It's a claim made by a charter school leader in the education documentary "Waiting for 'Superman,'" which places much of the blame for bad schools nationwide on union rules that protect incompetent teachers.

Mayor Michael Bloomberg announced on national television last week that he would overhaul the way city teachers are granted tenure, linking their advancement to improving student test scores.

"Just as we are raising the bar for our students through higher standards, we must also raise the bar for our teachers and principals — and we are," Bloomberg said.

But city teachers say that if bad teachers have won tenure protection it's the fault of the administrators who gave it to them.

"We don't make that decision. Whoever the principal is makes that decision," said LezAnne Edmond, a Manhattan high school teacher with 15 years of experience.

Teacher tenure has its roots in academic tenure, which was intended to protect academic freedom; once granted, professors are rarely fired. Tenure rules for K-12 teachers vary from state to state, with some operating more like universities and others that offer no stronger protection than job security laws that prevent people from being fired without cause.

States including California, Florida and Colorado have passed or proposed legislation to change tenure laws in hopes of securing education funding under President Barack Obama's "Race to the Top" program.

New York City teachers can win tenure after three years. Once they are granted tenure they cannot be fired without an administrative hearing. What the teachers union calls due process, Bloomberg and Schools Chancellor Joel Klein call a system that has protected incompetence.

The issue gained prominence with the Sept. 24 release of "Waiting for 'Superman,'" opening to wider release on Friday. The documentary from "An Inconvenient Truth" director Davis Guggenheim suggests that kids receive a superior education in charter schools without unions.

NBC's Sept. 27-28 education summit covered much of the same ground. Bloomberg used a 15-minute MSNBC segment to announce a tenure crackdown.

"We'll do more to support teachers and reward great teaching, and that includes ending tenure as we know it," he said. Bloomberg said principals must start denying tenure unless their students have made two years of progress on state tests.

Michael Mulgrew, the president of the United Federation of Teachers, responded that principals can already deny tenure "for any reason" and that teachers "would welcome an objective tenure-granting process based on agreed-upon standards."

But the union has opposed using state test scores — the city's preferred benchmark — to measure teacher performance.

City Department of Education spokeswoman Natalie Ravitz said the union is being disingenuous.

"On one hand, they seem to be blaming principals for too many teachers getting tenure," she said in an e-mail. "On the other hand, they don't want principals to take into account student performance when making tenure decisions."

This year, 3.7 percent of teachers who reached the end of their three-year probationary period were denied tenure, up from 2.3 percent the year before. Another 7.2 percent saw their probation extended by a year.

Ernest Logan, president of the union representing New York City principals, said his members take student achievement into account.

"I don't think people are just granting people tenure because they've been there three years," Logan said.

Veteran city teachers say they need tenure for job security and to protect the First Amendment rights it was designed to safeguard.

"I need tenure to speak out," said Arthur Goldstein, a union chapter leader at Francis Lewis High School in Queens.

Goldstein said he has complained publicly about overcrowding and other issues.

"I'm standing up for the kids of Francis Lewis High School and I absolutely need tenure," he said.

Katharine Dawson, who retired last summer after 12 years as a city schoolteacher, said tenure "protects you from favoritism, it protects you from all kinds of things."

Asked about tenure protecting bad teachers, she said, "Maybe there's two bad teachers per school. Is it worth throwing the baby out with the bathwater?"

One teacher whom Bloomberg would like to throw out is Melissa Petro, whose essay about using Craigslist to sell herself as a prostitute was published in the Huffington Post on Sept. 7, the same day she was awarded tenure by the principal of her Bronx elementary school.

Bloomberg demanded that Petro be pulled from the classroom, but she has tenure and cannot be fired without due process. She has been assigned to an office job pending an investigation. A phone number for Petro could not be found.