S.D. Codified Laws § 5-11-2
The county auditor of each county having within its boundaries school and endowment lands shall ascertain the average assessed valuation per acre of all taxable agricultural lands within the county, after the assessment of such lands have been finally equalized by the boards of equalization and shall multiply such average assessed valuation by the number of acres of school and endowment lands and the resultant figure shall be added to the assessed valuation of such county to arrive at the rate of tax levy in mills for the county. Provided, however, that the amount ascertained by the county auditor as representing the value of school and endowment lands shall not be included or considered in determining the assessed value of any county or school district for any purpose whatsoever, except as herein expressly provided in establishing rates of levy.
SDCL 5-11-2