The head of the union that represents teachers in the Detroit school district said he opposes any attempt to provide salary boosts to some teachers over others, including through merit pay.

That comes two days after Detroit Schools Superintendent Nikolai Vitti, in a State of the Schools address, called for higher salaries for teachers (and some principals) who see improvement in their students’ academic performance, a method generally known as merit pay or performance-based pay. Vitti also called for higher pay to attract teachers to jobs in hard-to-staff schools.

“The union is fundamentally against merit pay,” Terrence Martin, the president of the Detroit Federation of Teachers, said Friday. It’s something, he said, the union has previously fought against.

The discussion is complicated by state law, though, which requires school districts to adopt merit pay as part of their compensation system for teachers and administrators.

“The reality is the law says what the law says,” Martin said. “We’re going to abide by the law.”

But he said the union would fight against any other efforts to treat some groups of union members differently.

Vitti has previously said he’s committed to raising salaries for teachers at the top of the pay scale, in an effort to get their salaries to where they were when the state began appointing emergency managers to run the district. During emergency management, which began in 2009 and continued until the end of 2016, teachers in the district had their pay reduced and loaned the district money.

“We believe there is a way to accomplish the need to increase pay for our most veteran teachers at pre-emergency management levels, significantly increase less veteran teachers pay, and separately but not as a substitution of the latter, add performance pay for individual teachers and teams at schools that dramatically improve student achievement,” Vitti said in a statement.

Martin said the union’s priority is “to make sure we take care of and impact in a positive way the entire group, the entire workforce. Those are the things we are working on at the bargaining table.”

The current contract included a salary increase of seven percent over the first two years, and required a contract re-opener in the third year to negotiate pay for the third and final year of the contract.

“I don’t think we can truly move the school district forward in a positive way and impact students the way we need to, and raise student achievement, if we begin to parse out different groups. We have to collectively show that we are serious about stabilizing the workforce.” Treating some groups differently, he said, “pits different groups against each other.”

When two district teachers made similar arguments at a recent community meeting, Vitti said he agreed with the argument. And he urged them to fight for equitable funding from the state that would allow the district to pay all teachers what they deserve.

He reiterated that during his address Wednesday.

On social media, teachers have been staunchly against the idea of merit pay. One said, “I don’t like this one bit.” Another said she’d be willing to consider it only “if I was guaranteed a child’s attendance were not held against my ability to help a child show growth.”

“Merit pay based on test score data will always lead to teachers who teach under the most adverse conditions being left out of the ‘rewards.’ “ said William Weir, who retired last year as a teacher in the district and is now active in a community education advocacy group.

Merit pay has been a divisive issue across the country. Dissatisfaction with a 15-year-old merit pay system in Denver Public Schools was at the center of a dispute that led to a three-day teacher strike in February.

In Detroit, the negotiations are ongoing to settle pay for the third year of the contract. Martin said, “We are making some strides in some places and at some places we’re at a crossroads. The union is interested in getting something done, and doing something that is fair for all members. However long that takes, that’s how long it takes.”