Mont. Code Ann. § 20-6-307

Within 6 months after a high school district fails to operate an accredited high school within its boundaries for a period of 1 year, the county superintendent shall order the high school district abandoned. At least 20 days before issuing an abandonment order, the county superintendent shall notify the trustees of the high school district of the impending abandonment. When the order is issued, the county superintendent shall also order the attachment of the territory of each elementary district of the abandoned high school district to another high school district or districts of the county or, with the consent of the county superintendent of an adjacent county, to another contiguous high school district or districts in the adjacent county.