TOPEKA, Kan. (AP) - The largest teachers' union in Kansas has filed a lawsuit against a new state law that ended guaranteed tenure for public school teachers.

The Kansas National Education Association argued Monday that the law violated the state constitution for the anti-tenure policy to be added to a larger education funding measure.

The lawsuit filed in Shawnee County District Court alleges the Republican-dominated Legislature violated a provision of the state constitution requiring most bills to contain only one subject.

However, the 23,000-member union is asking a judge block only the anti-tenure provision.

The measure approved by legislators in April boosted state aid to poor school districts by $129 million for the new school year. Conservative GOP legislators insisted on tying the new funding to other policy provisions, including the one on tenure.

Gov. Sam Brownback called the KNEA lawsuit an exercise in labor union politics.

"Kansas has high quality, well-funded schools and I signed HB 2506 to keep it that way," Brownback said in a statement. "I am concerned this misdirected lawsuit may cast doubt on, or unwittingly endanger, school funding just as classrooms are convening all across Kansas."

(Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)