Schools Chancellor Joel Klein argued before the City Council today that firing teachers, perhaps en masse, is the only strategy left to handle expected budget gaps next school year. “There is very little fat left to trim,” Klein said, discussing a gap that his top budget official said will be at least $600 million and at worst $1.2 billion.

It’s still unclear whether state budget cuts to education will necessitate layoffs at the scale Klein described — a total of 8,500 teachers in the most draconian scenario. The state legislature is working towards an April 1 deadline to pass a budget, and while the Senate and governor’s proposed budget would cost the city schools more than $400 million at a minimum, the Assembly is reportedly planning far less severe cuts.

But at the City Council today Klein stuck to his doomsday predictions, outlining how the 8,500 layoffs would hit each school district. Under the state’s current “last in, first out” method of cutting the most recently hired teachers first, neighborhoods from the South Bronx to the Upper East Side — which have the highest density population of younger teachers, due mainly to either high turnover rates or enrollment spikes — would lose nearly a fifth of their teachers immediately next year, Klein said.

Eight other districts in those areas, mainly in Manhattan and the Bronx, would all lose more than 15 percent of their teachers to layoffs. (The Department of Education’s full list of how each district would be affected by layoffs is below the jump.)

Testifying after Klein, teachers union president Michael Mulgrew argued that mass firings are unnecessary, even under severe budget cuts. He accused the chancellor of exploiting the city’s dire financial situation to achieve the political end of changing the city’s hiring and firing practices, a strategy he called “distressing.”

But Klein characterized the DOE’s fiscal situation as so dismal that officials have no choice but to fire teachers. Half of the DOE’s $22 billion budget is comprised of costs the department cannot control, like pensions and debt obligations. Central administrative costs have been reduced to three percent of the DOE’s budget, Klein said, and cannot be reduced much more without hurting schools — an argument critics will no doubt contest. The remaining $8 billion is controlled by principals, who spend most of that money paying teachers.

Klein and Mayor Michael Bloomberg are aggressively lobbying Albany to change the last-in first-out policy. Today Klein argued that the requirement forces schools not only to fire outstanding younger teachers, but also to make layoff decisions without regard to teachers’ expertise and individual schools’ needs.

He forecast a huge shuffling of teachers from school to school, as teachers at schools that are not eliminating teacher positions but who are the most junior in their districts are fired and replaced by older teachers. “What you get is this bumping musical chairs effect which is chaotic across the board,” Klein said.

Klein also argued that the firing regulations will lead to increased class sizes because the city will be forced to fire more teachers for the same savings. (For the same amount of savings, the system could either fire a single, expensive senior teacher or several less expensive junior teachers.)

Council Member Lewis Fiddler countered that Klein’s line of thinking creates an incentive to fire older teachers. “Aren’t you putting undue pressure on principals to lay off the most senior teachers?” Fiddler asked.

Klein replied that a better system of teacher evaluations would prevent outstanding senior teachers from losing their jobs.

“Schools are held accountable, so they’re not going to lay off their best senior teacher,” Klein said.

Here are the city’s estimates for the percentages of teachers each district could lose, based on how principals have chosen to excess teachers in the past. Note that although the column says “percent positions lost,” the chart actually tracks the number of current teachers in each district who would risk losing their jobs. If layoffs do happen, it hasn’t yet been determined exactly how schools would lose their most junior teachers, DOE spokeswoman Ann Forte said today. But in any layoff scenario, districts that have hired more teachers in recent years — hard-to-staff districts with lots of turnover and the districts that have seen large spikes in enrollment — would be most disrupted.