The Denver teachers union used state law to make a public records request for the names, email addresses, and salaries of every charter school teacher in the school district — and Denver Public Schools complied and turned over the information.

The request could signal that the union plans to try to get charter school teachers to join. Currently, only teachers at district-run schools belong to the Denver union. Given that more than a quarter of Denver’s 200 schools are charters, recruiting charter school teachers could significantly swell the union’s ranks and increase its political power.

Some charter leaders, though, see unions — and the teacher contracts they negotiate — as a threat to the flexibility they say makes charter schools successful.

The Denver Classroom Teachers Association declined to say how it plans to use the charter teachers’ contact and salary information. Denver Public Schools officials recently sent an email to charter school leaders in the district giving them a heads-up about the request.

Colorado doesn’t have unionized charter schools, though they do exist in other states. In Chicago, teachers at two charter networks recently voted to authorize strikes if negotiations break down; these strikes would be the first of their kind in the nation.

A study by the National Alliance for Public Charter Schools found that 781 charter schools nationwide participated in collective bargaining agreements with teachers unions in 2016-17, which represented about 11 percent of charter schools nationwide. However, a majority of those were required by state law or district policy to be part of the contract.

The country’s two largest teachers unions — the National Education Association and the American Federation of Teachers — have welcomed charter school educators.

The Denver union is affiliated with the National Education Association, which did not respond to requests for comment for this story. On its website, the NEA says charter school educators “face many of the same issues public school teachers face, and they know the strength in having a unified voice to advocate for their students’ needs.” (Charter schools are public schools. The difference in Colorado is that they are run by nonprofit organizations instead of school districts.)

But many charter leaders suspect an ulterior motive, given that teachers unions are often the loudest opponents of efforts to open new charter schools or provide them with more funding.

“The unionization thing is within a broader set of strategies to destroy charter schools,” said Todd Ziebarth, senior vice president of the National Alliance for Public Charter Schools.

Teacher contracts often dictate how many days per year and hours per day teachers can work, an approach Ziebarth disparages as “one-size-fits-all.” One of the key tenets of charter schools is that they’re free from such requirements, and thus able to innovate in ways they believe will benefit students. Having to abide by a contract “doesn’t allow schools to make nimble decisions to improve learning for kids,” Ziebarth said.

The Colorado League of Charter Schools, a nonprofit membership organization for charter schools in the state, echoed some of the same sentiments in a statement that says, in part:

“It would be interesting that an organization that has historically worked so actively against the interests of charter schools, their teachers and their students — being one of the most outspoken voices at the State Capitol each year in opposition to more fair and equal funding for charter public schools and their students — would now be trying to position themselves as a partner.”

Last year, the Colorado Education Association — the statewide union to which the Denver teachers union belongs — opposed a bill in the state legislature that would have required school districts to share with charters a portion of locally approved tax increases.

When the bill was killed, the statewide union sent out a celebratory press release.

“Our state representatives made the correct move in rejecting this piece of legislation that blatantly favored unfettered charter schools at the expense of the vast majority of students attending public schools all across the state,” the union president said in the release.

Lawmakers eventually adopted a compromise that included the revenue sharing, plus new requirements that charters post more financial and operational information online. This time, the union’s press release only briefly mentioned the revenue sharing, while lauding the new rules.

“Parents at Rocky Mountain Prep, where (the bill) was signed, will finally be able to go to the school’s website and easily see the school’s 22 statutory waivers, including the school’s waiver from the requirement that classrooms have licensed, certified teachers,” it said.

Rocky Mountain Prep is one of several homegrown charter networks in Denver. Founder James Cryan said he was aware that the Denver teachers union had made the public records request, but he didn’t have any more information. Other charter networks said the same.

Ahmed White, a University of Colorado Law School professor who specializes in labor and employment law, said getting employee lists is a common practice in union organizing.

“That’s a logical thing for them to do,” he said of the Denver teachers union’s public records request. “If I were them, I would have done that too because you’ve got a lot of employees and no other reasonable way to get a hold of their information.”

Chalkbeat used the state public records law to get a copy of the information the union received in its request. It is a spreadsheet with the names of 1,668 charter school teachers, social workers, counselors, and psychologists. It lists where each of them works, how many days per year they’re contracted to work, and their hourly salary.

Charter school teachers are often paid less than district teachers. A 2016 report by the Colorado Department of Education found that the average charter school teacher salary in the previous year was $39,052, whereas the average salary at a district-run school was $54,455.

It was not immediately clear based on the information in the spreadsheet how Denver charter teacher salaries compare to the salaries of teachers at district-run schools. The average teacher at a district-run school in Denver made $57,753 last year, according to the district.

A spokesperson for one Denver charter network said the hourly salaries listed in the spreadsheet for at least some of its teachers were not accurate or up to date.

The spreadsheet also includes an email address for each teacher. But it is a Denver Public Schools email address, not the address given to them by their charter school. A district spokesperson said charter school teachers have district email addresses so they can access the online systems the district uses to record things like grades and attendance.

A spokesperson for the Colorado Education Association said the Denver union acted on its own in making the request, and it is not part of a statewide strategy to unionize charter teachers.

The Denver union had about 3,000 members last year. It is currently in negotiations with the district to revise the district’s pay-for-performance system.