A district may at any time pay the entire principal or part thereof and interest then due on a note or contract held by the state, out of any moneys not needed for school purposes. The district may issue and sell its refunding bonds in accordance with chapter 475, for such purpose, by actions of its school board and without the necessity of a vote by its electors, if such refunding bonds plus its net debt does not exceed the debt limit prescribed by chapter 475. Any such refunding bonds may bear interest at a rate or rates higher or lower than the rate payable on the loan or loans refunded thereby.