DENVER — Denver's first teacher strike in 25 years extended into a third day Wednesday, after a marathon bargaining session Tuesday that ended around 11 p.m. with some signs of progress around the central issue of teacher pay structure.

This strike is only the latest in the long and growing list of public school teacher walkouts in the U.S., but it's the first one focused on merit pay. The Colorado capital was one of the first cities in the country to introduce, in 2005, a system of bonuses and incentives tied to student-test performance and other metrics. But teachers here say the system, known as ProComp, soon became an excuse for the district to pay them less to begin with, causing their salaries to stagnate when compared with Denver’s fast-rising cost of living. Membership in the union has exploded in the past few years.

“It’s been a struggle to finally feel like I have my feet under me — and barely,” said Rebecka Hendricks, a 33-year-old high school teacher and member of the union’s bargaining team. “I still have to have a roommate. I’ve had several extra jobs: I used to drive Lyft, I used to deliver food for Postmates, I used to sell things on eBay. I did whatever I could to get extra money to just be able to make it that month.”

Denver teachers complain that the bonuses they get under ProComp are often arbitrary and unreliable, making their take-home salaries fluctuate wildly from year to year. That’s why they’re asking for a simple salary structure with regular and predictable raises.

The school district has acceded to many of the union’s demands, agreeing to simplify the system and to put an additional $20 million into teacher pay. But it has also insisted on putting even more money into certain incentives, including a bonus for teachers who work at high-poverty-area schools.

In the years after Denver implemented ProComp, similar systems spread to several major cities, and the Obama administration made it a requirement for federal grants under its Race to the Top program. The strike in Denver is a sign that teachers around the country are revolting against the core tenets of the school reform movement.

“It’s kind of a corporate idea, right? You pay people bonuses to incentivize certain behavior,” said Jeff Buck, a high school teacher and union member who helped design and implement ProComp but now repudiates the program. “But we’re not in a for-profit situation. This is a human services organization. And people are absolutely driven, and some are motivated by money, but I think, for the most part, people understand that we’re not here to get rich.”

This segment originally aired February 12, 2019, on VICE News Tonight on HBO.