Bonds issued under this subpart may be exchanged for not less than an equal principal amount and accrued interest, if any, of indebtedness to be retired thereby, including indebtedness not yet due, if such indebtedness is then redeemable or if the holder thereof is willing to surrender the indebtedness for retirement, but otherwise shall be sold and the proceeds thereof shall be applied to the payment of such schoolhouse bonded indebtedness or accrued interest due or redeemable which may be so surrendered.
OCGA § 20-2-471