ST. PAUL — A Ramsey County judge has dismissed a lawsuit that challenged Minnesota’s teacher tenure laws.

A group of Minnesota parents and national education reform groups sued last spring, maintaining that the laws giving layoff protection to teachers after three years on the job protect ineffective teachers.

The plaintiffs alleged the laws are unconstitutional, perpetuate Minnesota’s achievement gaps and prevent efforts to improve the state’s public school system.

State Education Commissioner Brenda Cassellius said the laws protect teachers’ due process while still giving school officials the authority to remove teachers. The state’s teachers’ union said tenure rules give teachers due process against arbitrary firing.

Judge Margaret Marrinan on Wednesday ruled that the lawsuit failed to establish a link between low academic achievement and the due process provided by the tenure laws.