Roughly 60 percent of 4,662 eligible city teachers were approved for tenure this year. That's a little higher than last year's approval rate of 53 percent, but enough of a change to prompt debate about whether Mayor Bill de Blasio was tough enough on teachers.

Four years ago, Mayor Michael Bloomberg's administration made it harder for teachers to get tenure by extending their probationary periods. In the 2009-10 school year, 89 percent of teachers received tenure after a three year probationary period. The following year, that rate fell to just 58 percent and it continued to fall.

This year, nearly 38 percent of teachers had their probation extended compared to 44 percent in the 2013-14 school year. And 93 teachers had their tenure outright denied, which is 2 percent of all who were eligible compared to 3 percent in recent years.

Chancellor Carmen Fariña emphasized the importance of strong teachers in every classroom:

"Retention of quality teachers is an urgent priority and the teachers’ contract allows us to do this better, and at the same time, the methodology for helping someone out of the profession who does not belong in the profession is also better than it’s ever been," she said. "We have renewed our focus on professional development, with 80 minutes each week and sessions for teachers of all grades and subjects across the city, to ensure that we are supporting our teachers and helping improve their craft.”

New York State's teacher tenure law is now the subject of a lawsuit brought by two different groups, including one led by former television news anchor Campell Brown, who claim it allows too many bad teachers to continue working in classrooms. The two cases have since been consolidated and the teachers unions are asking a judge to dismiss the case.

United Federation of Teachers spokeswoman Alison Gendar said the numbers spoke for themselves. “So much for Campbell Brown’s claim that tenure is automatic.”

But Brown said the numbers prove the system of awarding tenure was broken.

"In fact, it violates common sense for a system to approve or extend tenure to nearly every teacher while two-thirds of their students remain without basic skills. It’s time we fix an education system that blindly moves forward with tenure while moving our students backward,” she said.

Eric Nadelstern, a professor of practice in educational leadership at Teachers College who served in the Bloomberg administration, also saw the uptick in teachers granted tenure as a step in the wrong direction.

"The question is how high should the bar be," he said, noting tenure wasn't a job guarantee but gave a teacher the right to due process. "My sense is it wasn't high enough when we got there, we tried to set it higher, we were in the process of setting it higher and now we've moved back to a lower bar."

The city is in the second year of a new teacher evaluation system, meaning it's still too soon to tell whether it's made an impact because teachers need two ineffective ratings in a row in order for the city to seek dismissal, barring other circumstances.