Chicago teachers have shown their solidarity in massive numbers. More than 90 percent of teachers have given the OK for a work stoppage, multiple sources told NBC Chicago.
That number is well above the 75 percent needed, by law, to authorize a strike.
Chicago Teachers Union spokesman Stephanie Gadlin declined to provide an official number but said that some schools have seen 100 percent of teachers approve a strike.
"We're pleased," she said, but added: "We know there will be challenges by [Chicago Public Schools].
CTU is analyzing and double-checking the numbers before releasing any information on the vote. That may happen Monday.
CPS officials declined to comment until official numbers are released.
The strike authorization vote began Wednesday. CPS and CTU are currently in contract negotiations but are far apart when it comes to teacher pay and how teachers will be compensated for longer school days.
Mayor Rahm Emanuel last year rescinded a four percent pay increase and pushed for a longer school day. CPS has since proposed a five-year contract which guarantees teachers a two percent raise in their first year and lengthens the school day by 20 percent.
CTU is pushing for a two-year contract that would reduce class sizes and give teachers a 24 percent raise in their first year and a five percent raise the second year.
"This is a reflection of the treatment we as teachers have been subjected to this year," David Rose, a teacher at Roberto Clemente Community Academy said. "The posturing of the board of education has created such misery and suffering and discontent that we needed to send a message."
Schools CEO Jean Claude Brizard has pleaded with the union to hold off its vote until an independent consultant releases its report July 16.
Financial reports show the school system has a $700 million budget shortfall.
Any possible strike would not take place until September.
Editor's Note: This post incorrectly reported the percentage by which the teachers' school day would be lengthened. The post has been updated.