The argument that heated up today between city officials, Governor Andrew Cuomo and members of the state legislature over abolishing the state’s seniority-based layoff system for teachers essentially boils down to one thing: timing.

Mayor Michael Bloomberg and Department of Education officials want to do away with the “last-in, first-out” system immediately so that they can use new criteria to lay off teachers at the end of this school year. Cuomo and other state officials — several of whom support changing the layoff system generally — counter that abandoning seniority-based layoffs must wait until the state has a better system it can use instead.

Yesterday, Cuomo introduced a bill that would speed implementation of the teacher evaluation bill that Albany passed last May up by a year but did not propose any changes to the layoff system. City officials immediately blasted the bill as “a sham” and a distraction, and Bloomberg said today the governor’s proposal “simply kicks the can down the road.”

Part of the disagreement lies in whether or not the city and the state have time to kick that can. City officials speak of the need to change the layoff system with a sense of urgency, arguing that a budget crisis necessitates laying off more than 4,000 teachers this year.

But many people — including the teachers union, the governor and some state legislators — are skeptical of the mayor’s timeline. The union accuses the city of scare-mongering and argues that the city has the funds to preserve teachers’ jobs. The governor has said that his proposed cuts to education funding also should not prompt teacher layoffs this year.

“There are many in the legislature who are not convinced that the mayor’s layoff threats are real,” said Assemblyman Hakeem Jeffries. “Over the last several budget cycles, the mayor has threatened layoffs that have never come to pass.”

Jeffries said that he was willing to consider changing the seniority-based layoff system. But he said that he is not willing to grant the city greater flexibility in choosing which teachers to fire before a more objective system is put in place. And he said that he is not yet convinced that the city does not have the time to develop that system.

“To what degree is the layoff threat real? Is there reserve funding sufficient to prevent layoffs? What amount of additional state funding is necessary to ensure that not a single teacher is laid off this year?” Jeffries said. “This information will be necessary for the legislature to make any sort of informed decision over the coming weeks.”

Cuomo has said repeatedly that he believes that merit should eventually be a factor in determining which teacher lose their jobs. His bill is meant to address the concern — voiced by critics of the mayor’s push to lay off teachers based on merit rather than seniority — that the city and state do not yet have a reliable method to determine “merit.”

Critics of State Senator John Flanagan’s complex bill, which is backed by Mayor Michael Bloomberg and passed the Senate yesterday, argue that it relies too heavily on principal’s subjective evaluations of teachers, which in some documented cases have been abused.

“It is time to move beyond the so-called ‘last in, first out’ system of relying exclusively on seniority,” Cuomo said last night in a statement. “However, we need a legitimate evaluation system to rely upon. This will help make a statewide evaluation system ready and allow us to replace ‘last in, first out.'”

City officials and opponents of seniority-based layoffs countered today that abandoning “last-in, first-out” cannot be done incrementally as the teacher evaluation system improves.

Joe Williams, the head of Democrats for Education Reform and one of the most outspoken critics of the current layoff system, said he agreed with the governor that a robust and fair evaluation system should be put in place. “However, that system must be instituted alongside a crystal clear law that eliminates [last-in, first-out] and forces merit to be taken into account when laying off teachers,” Williams said.

Under the original evaluation law that Cuomo wants to change, only teachers of tested grades and subjects would start receiving rankings next school year. If Cuomo’s amendment is passed, all teachers in all grades would be ranked next year.

That would mean that by next year, state and local districts will need to come up with a system to judge student growth in all grades and subjects that currently don’t have standardized tests. State officials are currently developing regulations to guide those new measures; the bill gives officials a June deadline to complete those guidelines.

But the original evaluation law also requires districts to negotiate parts of how they will measure student growth with their local unions, and Cuomo’s bill is silent on those negotiations. City officials argued today that could allow the new evaluations — and therefore, a merit-based layoff system — to be delayed if negotiations stall.

“The acceleration of the timelines in the bill is artificial, as districts and unions are not compelled to change their current evaluation process until they’ve successfully negotiated new collective bargaining agreements,” wrote Deputy Chancellor John White today in a memo released to reporters.