Less than two years after pledging that he did not want to end tenure, Mayor Bloomberg struck a different chord today.

“Do I think it’s needed at the public school level? No,” he said today.

The statement came days after Bloomberg’s most recent escalation in rhetoric against tenure protections. During his weekly radio address last week, he said tenure is a vestige of the McCarthy Era of the 1950s, when teachers were persecuted for their political views.

But until today he had not said outright that he opposed tenure’s existence for public school teachers. In fact, in a Nov. 2009 speech at the Center for American Progress in Washington, D.C., he declared, “Let me be clear: We are not proposing an end to tenure.” Last year, Bloomberg promised “to end teacher tenure as we know it,” but by making it tougher to achieve, not doing away with it. That vow appeared to bear fruit this year when the number of city teachers awarded tenure fell dramatically.

Bloomberg was responding to a question I asked about what protections he thinks teachers should have given that Schools Chancellor Dennis Walcott made clear that people who observe cheating should report it. Some teachers say they have been harassed or given low ratings after speaking out about labor conditions or problems within their schools.

Bloomberg said today that civil service protections and the First Amendment of the Constitution are sufficient to protect those teachers.

“I think the United States’ First Amendment protects people generally,” he said.

New York Post columnist Michael Goodwin asked teachers to reach out to Walcott with cheating after the chancellor told him that he wanted to root out cheating. Already, the call for whistleblowers has yielded emails that have in turn spurred investigations.

Today, Walcott dialed back Goodwin’s enthusiasm, saying that the department would investigate all cheating claims but that he had never called on teachers to come forward with allegations.

“I’m a person who wants to make sure we have a system that is honest, which it is,” he said. “And so there’s no public call where I want you to out your principal, I want you to out your assistant principal. I want to be very clear about that. It’s up to all of us to make sure that any cheating that’s taken place at any level, that we know about it because we will follow up.”