Opening a new front in the assault on teacher tenure, a group of parents backed by wealthy philanthropists served notice to defendants on Wednesday in a lawsuit challenging Minnesota’s job protections for teachers, as well as the state’s rules governing which teachers are laid off as a result of budget cuts.

Similar to cases in California and New York, the plaintiffs, who are filing the lawsuit in district court in Ramsey County in St. Paul, argue that the state’s tenure and layoff laws disproportionately harm poor, minority children because, they say, the most ineffective teachers are more likely to be assigned to public schools with high concentrations of those children.

In the lawsuit, parents of children in public schools across Minnesota argue that the state’s tenure laws, which grant teachers job protections after three years on the job, deprive students of “their fundamental right to a thorough and efficient education” under the state’s Constitution. The suit also argues that state laws that protect the most veteran teachers in the event of layoffs can result in better teachers losing their jobs simply because they have fewer years in the classroom.

As in California and New York, the suit is likely to be fought fiercely by teachers’ unions and other groups that say teacher job protections do not cause educational inequity or lead to underperformers remaining in the classroom.