Negotiations grew more tense between the Denver teachers union and the district on Tuesday as the two sides struggled to find common ground over its pay-for-performance system.

Union and district officials appear to literally be at standstill. After a tense exchange before noon, district officials departed the room to regroup — and did not return to the negotiating table. Talks are scheduled to resume Thursday.

The day’s developments indicate that it may be growing more difficult for Denver to avoid a strike that would upend Colorado’s largest school district and add to a national wave of teacher activism.

On Tuesday morning, Denver Classroom Teachers Association representatives told district leaders that they want a traditional salary schedule, with “steps” corresponding to a teacher’s experience and longevity and “lanes” representing education. The district’s proposal, which would allow teachers who served 10 consecutive years to jump into the next lane, was unacceptable, the union said, and they don’t plan to budge.

“We need you to convert your structure to ours so we can move forward,” said union bargaining representative Robert Gould.

Asked what kind of changes the union might still be open to, Gould responded, “You’re not listening. You’re not listening to what we’ve been saying for the last two weeks, you haven’t been listening to what we’ve been saying for the last two months, you haven’t been listening to what we’ve been saying the last year, nor the last five years. What we’ve been saying is, we need the structure to be our structure. Then we can move forward.”

A long pause followed.

“Well, I don’t honestly know where we go from this ultimatum here,” said Michelle Berge, the district’s general counsel, adding that her team would regroup.

Then Gould continued.

“Denver teachers, they’ve met their limit,” he said. “There’s only so long you can continue to tell people no. And at some point, that’s what you’re going to get back — no. This Saturday, teachers are going to vote. They’re either going to vote yes for a commitment or they’re going to vote yes for a strike.”

“I understand that,” Berge said, explaining the district is struggling to find a way forward when the union hasn’t agreed to changes in months.

Then the room erupted with union supporters noting changes they had agreed to.

“Cut more central administration waste!” parent and education activist Amy Carrington yelled.

District officials said they were cutting central administration. Seven million dollars is being cut, and more is coming, they said.

As talk shifted back to the union, Pam Shamburg, DCTA executive director, said it was time for bigger change.

“The reckoning has come,” she said. “The district is going to have to dig deep. But it’s going to have to happen. And now is the time for the reckoning.”

The two sides went into a break — and didn’t meet again.

District officials said Tuesday evening that they are processing the union’s position and have work to do before Thursday.

Superintendent Susana Cordova told Chalkbeat district officials entered Tuesday’s negotiations feeling they had come a long way toward the union position. Cordova said the district remains committed to making a deal, but would still like to get a counter-proposal from the union.

“We would like to see something from them,” said Cordova, who took the district’s top job last month. “I am new to negotiating, but that’s generally how that works.”

On Friday, Denver Public Schools officials presented a new proposal that would put an additional $6 million into teacher pay. That’s on top of the additional $17 million the district had already proposed, for a total of $23 million more.

Corey Kern, the union’s deputy executive director, said the two sides need to reach a “fundamental understanding” of how a teacher can qualify to move up “lanes” and potentially earn more money.

“If not, it will be very difficult for us to make a counter to the district,” he told Chalkbeat. “We would like to get back to the table and work on the issue and come to an agreement. But right now, we’re so far apart.”

The union is pushing for teachers to be able to move up in the system not just if they have earned master’s degrees or doctorates, but from other avenues, such as taking taking college courses or completing district professional development units, he said.

Mark Ferrandino, chief financial officer of the Denver district, said steps and lanes have become a sticking point in part because of how much money it would take to fund the different proposals but also because of philosophical differences. The district believes its proposal actually allows for more flexibility for teachers, while the “very clear table” provides much more transparency than the old ProComp system.

Kern said the union was disappointed the two sides did not reconvene Tuesday — “it felt like we lost a day” — but is hopeful for what’s next.

Cordova said she believes a deal remains in everyone’s best interests, but if one cannot be reached, she will do everything possible to keep schools open. That includes offering more money to substitute teachers, deploying other district staff to classrooms, and preparing lessons for those people to teach.

The union, for its part, is also encouraging parents to send students to school if there is a strike — with the intent of proving how hard it is to run schools without teachers.

Bargaining sessions are scheduled for Thursday and Friday, if necessary. Without an agreement, union leaders plan a strike vote for Saturday, and a strike could start as early as Jan. 28.

Eric Gorski contributed reporting.

Correction: This story has been updated to reflect that it was a parent, and not a union representative, who shouted, “Cut more central administration waste!”