(1)    Upon the petition of a school board of a district operating high school grades, the state superintendent, after investigation of the proposal, may transfer by order the entire school district from one agency to another, effective the next succeeding July 1. Any school district so transferred shall pay its agreed share of all expenses incurred by the agency in its behalf, but shall not be required to fulfill any commitments in the agency from which transferred extending beyond the effective date of transfer. A transfer of the territory of a union high school district shall include and effect a transfer of that territory of underlying elementary school districts which lie within the boundaries of the union high school district.

   (2)   When a new school district is created, it becomes a part of the agency in which the greatest portion of its equalized valuation lies, effective the next succeeding July 1. When territory is detached from a school district operating high school grades and attached to a school district that is in another agency, such transferred territory shall become a part of the agency of the school district to which it is attached, effective the next succeeding July 1.