Three former governors, as well as Colorado Governor Bill Ritter—three Democrats and one Republican—have co-written an editorial expressing their support for the reform of Colorado laws governing tenure for public school teachers. They’re also backing a controversial proposal to tie tenure to student performance (via the Denver Business Journal).

The state teachers’ union has strongly questioned the proposal, and now, it seems state lawmakers could delay enactment of the proposal for two years, according to The Associated Press. But the Senate Education Committee will hear more testimony on the bill today.

Currently, teachers’ jobs are protected after three years in the classroom, but according to the bill, as of 2013, educators whose students’ performance has improved for three years would be able to earn tenure.

Another potential snag for the bill is its price tag—about $240,000 to implement, reports The Denver Post, citing non-partisan fiscal analysis by state legislative staffers.