S.D. Codified Laws § 13-26-9
A decision by a school board to schedule the opening day of classes before the first Tuesday following the first Monday in September may be referred to a vote of the qualified voters of the school district by the filing of a petition signed by five percent of the registered voters in the school district, based upon the total number of registered voters voting at the last preceding general election, for districts with more than five thousand registered voters. Petitions in districts with less than five thousand registered voters must be signed by five percent of the total number of registered voters at the last preceding general election. The board in scheduling the opening day of classes shall allow sufficient time for the referendum process authorized in this section.
SDCL 13-26-9