A high school district may not be created and a high school district boundary may not be changed between the first day of January and the fourth Monday of August of any calendar year except when: (1) the entire territory of a high school district is annexed or attached to another high school district; (2) the entire territory or portion of a joint high school district located in one county is annexed or attached to another high school district; or (3) two or more districts are reorganized in their entirety.
Time Limitations For Boundary Changes
Mont. Code Ann. § 20-6-314, under High School Districts.
Mont. Code Ann. § 20-6-314