The board of the district maintaining a secondary school to which district is attached territory of districts discontinued by sections 123A.64 to 123A.72 must assume the duties and responsibilities of the board of the district so enlarged for the balance of the term to which the members were elected. At the next annual school election the successors to the members whose terms then expire shall be elected by the legally qualified voters of the newly enlarged district. Thereafter board members shall be elected according to the election procedure established for the election of board members in independent districts.