District bonds are legal and authorized investments for:
(1) banks;
(2) savings banks;
(3) trust companies;
(4) savings and loan associations;
(5) insurance companies;
(6) fiduciaries;
(7) trustees;
(8) guardians; and
(9) sinking funds of cities, counties, school districts, and other political subdivisions of the state and other public funds of the state and its agencies, including the permanent school fund.