The CTU's criticism comes as its rank-and-file face likely layoffs, as the school district battles a massive budget deficit.
The CTU is calling the legislation a bad deal for taxpayers.
Selling off Chicago's parking meters to a private company is known as one of the worst municipal deals in the city's history.
Then-Mayor Richard M. Daley managed to get 40 aldermen to support it, selling it as a quick cash fix. The CTU fears state lawmakers are about to go down the same path.
CTU Vice President Jackson Potter calls the "mega-projects bill" a parking meter deal on steroids.
"That has burned us in the past. As many Chicagoans remember, we don't want that to happen again. And this bill could do far worse," Potter said.
The bill gives major investors with projects worth more than $100 million a 40-year-long property tax break.
After it passed the Illinois House, Gov. JB Pritzker called on the state Senate to work with speed to get the deal done. Not only does it help the Bears with a new stadium, but Pritzker argues it will spur growth for all of Illinois.
"When companies come to Illinois, they go negotiate with local governments about their property taxes. And if they can't get a good deal, they go to another state. And so we're just trying to create a process for that to happen," Pritzker said.
The bill will create a standard for local governments to follow when negotiating tax breaks with companies. While the legislation will include some property tax relief for homeowners, CTU argues long-term tax deals for big companies take money away from schools.
"We can't balance school budgets on the backs of property taxpayers in order to help Amazon and Google, you know, stack their profits," Potter said.
CTU's effort to derail the bill comes at a time when Chicago Public Schools will likely lay off hundreds of teachers to balance an almost billion-dollar budget deficit. The Better Government Association says while the bill may result in economic growth, lawmakers have yet to provide an estimate of the long-term financial impact.
"We're kind of going to this without all the information. We need to know what the long-term consequences might be. And to point to the parking meter deal as kind of the worst case example of what could go wrong is not completely unfair," BGA President David Greising said.
As the state Senate works on the bill, their deadline is fast approaching. The legislative session ends May 31.
CTU leadership plans to be in Springfield calling for more revenue for schools on May 27.