We see plenty of political humor these days stemming from the policies and comments of New York City Mayor Michael Bloomberg, but not all of his ideas are suitable for satire. Back in 2010, the mayor proposed some remarkable changes to the public education system, including a plan to “end tenure as we know it.” That’s an ambitious goal to say the least, particularly in an environment with such a hugely powerful, deeply entrenched teacher union system. But just this week we found out that his efforts may be beginning to bear some fruit.

Nearly half of New York City teachers reaching the end of their probations were denied tenure this year, the Education Department said on Friday, marking the culmination of years of efforts toward Mayor Michael R. Bloomberg’s goal to end “tenure as we know it.”

Only 55 percent of eligible teachers, having worked for at least three years, earned tenure in 2012, compared with 97 percent in 2007.

An additional 42 percent this year were kept on probation for another year, and 3 percent were denied tenure and fired. Of those whose probations were extended last year, fewer than half won tenure this year, a third were given yet another year to prove themselves, and 16 percent were denied tenure or resigned.

This is an interesting trend which may be sending a message to the teachers’ unions, but it’s not a long term solution. Teachers failing to receive tenure are simply given another season or two to get it or they drop out. The end goal for all of them – and the unions – is still to land tenure so they can stay on indefinitely on the taxpayer dime once they get it.

It’s no surprise that that unions would be pushing back against this. We’re talking about a group which also fights like the devil against the idea of things like merit pay, despite the fact that studies show that it works. It’s a culture unlike virtually any other in the nation, where outrage greets the idea that competition for a job should result in the best candidates and that pay might be linked to performance.

If Bloomberg really wants to transition into a system with more long term potential, tenure should be gradually pushed back, taking five, ten and eventually twenty years, with a long term goal of eliminating the antiquated, self defeating system entirely. Of course, to do that will require essentially breaking the back of the current union power structure. And they’re not going to give up their long held positions of privilege without a fight.