Denver teachers and their allies were back on the picket line for a second day Tuesday as union leaders and district officials resumed negotiating over how teachers are paid.

The Denver Classroom Teachers Association began a strike Monday, its first in 25 years, over disagreements with Denver Public Schools about which teachers should receive bonuses, and how big those bonuses should be.

Catch up on the history of the pay system, ProComp, here and the current sticking points here. Talks between the union and district resumed at 10 a.m. Tuesday at the Denver Public Library’s central branch. They’re being livestreamed.

On Monday, advocates for students with disabilities filed suit against the Denver district, charging that those students would be harmed by a strike. Now, a conservative organization is threatening a second legal challenge.

From Chalkbeat reporter Melanie Asmar:

A conservative education advocacy organization has hired a lawyer and is prepared to file a lawsuit if the district and teachers union reach a deal that “violates Denver voters’ intent” when they passed a tax increase to fund the performance pay system known as ProComp, according to a press release sent by the group, Ready Colorado, on Tuesday afternoon.

Ready Colorado president Luke Ragland said in a statement that “it is clear the union is trying to undermine the goals and voter intent of ProComp.”

“The teachers union is trying to overturn the will of the voters, demanding the redistribution of funds approved to support high-poverty schools away from the neediest students,” Ragland said. “That is not what Denver voters signed off on.”

It’s worth noting that both the union and the district have attorneys who have reviewed their proposals. Leaders on both sides have said what they’re proposing meets the spirit of the ProComp ballot language.

We weren’t around in 2005 for that ballot initiative, so here’s some coverage from the time if you want to gauge voters’ intent for yourself.

This story was originally published by Chalkbeat, a nonprofit news organization covering public education. Sign up for their newsletters here.