S.D. Codified Laws § 13-26-2
The school board or governing body shall operate kindergarten through grade twelve in its schools. The school board shall operate grades one through twelve for at least a nine-month regular term in any one school year, and the number of hours in a school term for kindergarten shall be set pursuant to § 13-26-1. The regular school term may be conducted on a year-round basis and shall begin on a date established by the school board. The Board of Education Standards shall promulgate rules pursuant to chapter 1-26 governing the operation and scheduling of year-round schools. Any school board or governing body may release graduating high school seniors from school before the end of the regular term. A school is not required to make up time for school closing because of weather, disease, or emergency once it has reached the minimum number of hours in the school term as required by state law. Graduating seniors are excused from make up time if the make up time occurs after the students have graduated or after graduation exercises have been held. If classes have been convened and then are dismissed, or if classes convene at a time later in the day than normal, because of inclement weather, that day constitutes a school day in session equal to the number of hours planned for that day as established in the local school district calendar for the year.
School boards are encouraged to provide time within the regular school term for curriculum and staff development which shall be in addition to the time required in this section. Each school board shall determine the appropriate amount of time for this activity and how best to use the time based on local needs for program development, increased parent participation, student contact, teachers' preparation, or other needs of the schools in the district. School is in session only when classes are held and as provided in §§ 13-26-4 and 13-26-4.1. A school board may operate a special term during the summer months.
SDCL 13-26-2