Arizona public school teachers began voting Tuesday on whether to strike despite Republican Gov. Doug Ducey’s offer last week to raise their pay by 20 percent. The walkout vote is expected to be finished Thursday, with the results available that day.

Arizona Educators United, a union-backed umbrella group pushing for higher wages and education spending, called Ducey’s offer an “empty promise” because he has not detailed where the funds would come from. They also want funding for education increased by $1 billion overall, arguing that would address years of underfunding.