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DENVER — Denver teachers voted overwhelmingly Tuesday to go on strike after more than a year of negotiations over base pay.

Rob Gould, lead negotiator for the Denver Classroom Teachers Association, said 93 percent of unionized teachers voted in favor of a strike. The union represents 5,635 educators in the Denver Public School system, which could see a strike as soon as Monday.

"They're striking for better pay, they're striking for our profession and they're striking for Denver students," Gould said.

The main sticking point was increasing base pay, including lessening teachers' reliance on one-time bonuses for things such as having students with high test scores or working in a high-poverty school. Teachers also wanted to earn more for continuing their education.

Denver Public Schools Superintendent Susana Cordova said the district would turn to substitute teachers and administrators with teacher's licenses to keep schools open.

"At the end of the day, we know that we need our teachers back in our classrooms ... We remain open to continuing negotiations," she said.

While teachers have the right to strike in Colorado, the state can intervene. If the state steps in, the walkout could be delayed by up to 180 days, past the current school year.

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The state did not stop teachers in Pueblo from striking in May over pay after several years of tense contract talks. In that decision, the state labor department noted that it rarely uses its limited authority to intervene in contract talks unless requested by both sides.

Kate Martin, a former teacher and current employee of the Denver Classroom Teachers Association, unloads items for a potential teachers' strike outside the union's headquarters in south Denver last Thursday. David Zalubowski / AP

The Pueblo school district had asked for the state's guidance, but the union did not ask for intervention at all. Most of the city's 20 schools were shut down by the weeklong strike, which ended with teachers winning a 2 percent cost-of-living retroactive raise and a 2.5 percent increase in the current school year.

The union representing Denver's teachers gave notice of a possible strike Jan. 8, but state law requires them to wait 20 days before walking off the job.

DCTA President Henry Roman said the district's bonus system has changed dramatically since voters approved funding for it in 2005, leaving teachers dependent on earning bonuses for things that are largely outside their control. He said that has led to a high turnover rate for teachers seeking financial stability in districts with more traditional pay systems.

The union says the school district's offer fell $8 million short from the funding it wants to change the compensation system, an amount it claims the district could find by reducing administrators' bonuses and taking money out of its $64 million reserve.

"DPS has made its choice to keep critical funding in central administration, and not to apply more of those funds to the classroom where they would provide the greatest benefit for student learning," Roman said. "This vote shows their priorities are unacceptable to the majority of Denver teachers."

The school district said its offer would mean an average 10 percent raise for teachers in the next school year and make the minimum starting salary for teachers $45,500, the second-highest in the Denver area.

According to the district's website, the starting teacher salary is currently $39,851 and the average teacher salary overall is $50,449.

A statement from the district before the vote acknowledged that its proposed package was not enough, putting the blame on state funding, but urged teachers to compare the proposal to those at other nearby school districts.

"We agree with our teachers that this is not enough and we will continue to fight to address the inadequate funding of our education system in Colorado," Cordova said.

Janelle O'Malley stopped by negotiations last week to drop off letters from parents and grandparents of students at her son's high-poverty elementary school urging administrators to make their best offer now rather than after a possible strike to avoid forcing parents to miss work unnecessarily in case schools are closed.

Like many other parents at her school, she cobbles together arrangements with her husband and mother-in-law to drop off and pick up her son to fit around their work schedules. As a longtime retail store manager with a supportive team, she said she would have some flexibility to adjust her hours if her son could not go to school but she said many others caretakers there would not.

She sympathizes with teachers and thinks that those in a profession that requires a degree should be paid a professional salary that is predictable.

"There is money in the district. It's just not going to the right places," she said.

The Denver teacher vote came just after Los Angeles teachers voted to end a six-day strike after securing a 6 percent pay hike and a commitment to reduce class sizes.

Teachers hoped to build on the "Red4Ed" movement that began last year in West Virginia and moved to Oklahoma, Kentucky, Arizona, and Washington state. It spread from conservative states with "right to work" laws that limit the ability to strike to the more liberal West Coast with strong unions.