Form and denomination of bonds.

The district school board may prescribe the denomination of the bonds to be issued, and such bonds may be issued with or without interest coupons in the discretion of the board. The form of the bonds to be issued may be prescribed by the State Board of Education on the recommendation of the Department of Legal Affairs. The schedule of maturities of the proposed bonds shall be so arranged that the total payments required each year shall be as nearly equal as practicable. The schedule shall provide that all bonds are to be retired within a period of 30 years from the date of issuance unless a longer period is required and has been specifically approved by the Department of Education. All bonds issued under this section shall be callable at the times and upon the terms prescribed by the district school board.