Warren Consolidated Schools spokesman Robert Freehan said about 500 teachers have taken a personal day, and the suburban Detroit district will cancel classes for its 16,000 students.
Suburban Detroit's Taylor school district is also closed today.
Warren's teachers are represented by the Michigan Education Association.
Republican spokesman Matt Frendewey said thousands of students will miss class "because union bosses are afraid to give workers in Michigan a choice in their union representation."
Right-to-work laws bar unions from collecting mandatory fees from workers they represent under collective bargaining agreements.