All school districts are authorized and empowered to issue negotiable bonds for the following purposes only: to refund any bonded indebtedness which is or is about to become due and payable, or whenever such indebtedness can be refunded at a lower rate of interest; to fund any judgments or outstanding warrants, and to raise money for any purpose for which the school board is authorized to spend school district funds.
SDCL 13-19-7