All such notes or bonds shall be sold at not less than par at public sale after notice setting forth the terms and conditions of sale, published in such newspaper circulating in the school district, and in such financial newspaper, as shall be designated by any such resolution, except in the following cases:

a. If no bids are received at such public sale, or if all bids are rejected, any notes or bonds or part thereof may with the written assent of the commission be sold without further notice at private sale at any time within six months.

b. With the approval in writing of the commission, any notes or bonds or part thereof may be exchanged for any notes or bonds, including interest thereon, of the school district issued under this or any other law. The rate of interest borne by any such notes or bonds may be higher or lower than the rate of interest borne by the notes or bonds surrendered.

c. With the approval in writing of the commission, any notes or bonds may be issued directly to any creditor of the school district in absolute and unconditional payment of the indebtedness and interest thereon of such school district to such creditor, provided that notes or bonds shall not be so issued unless and until the amount due such creditor has been determined by the board of education and by the commission, nor unless and until the school district receives from such creditor a release running to the school district and if such creditor is a party plaintiff in any suit, action or proceeding pending against the school district relative to such indebtedness, a stipulation of dismissal of such suit, action or proceeding. Such release and such stipulation shall be approved as to form by counsel to the school district and by counsel to the commission.

d. Any notes or bonds, or any part thereof, may be sold without any previous public offering to, and be purchased by, any sinking fund commission or the insurance or pension fund commissioners of the school district offering the bonds, or be sold to any board, commission or officers of the state, authorized by law to purchase such notes or bonds.

e. Any notes or bonds payable not more than seven years from their date may be sold at private sale with the written assent of the commission.