A handful of South Dakota voters once decided school start dates for the entire state; now local boards or local voters choose

In 1985, by a margin of 282 votes (0.1%), South Dakota voters approved a citizen initiative—Initiative 2—requiring public schools to start the school year after Labor Day.
In 1993, the state legislature altered Initiative 2 and repealed the requirement that the school year start no earlier than the first Tuesday after the first Monday in September. The 1993 law allowed local school boards to determine school year start dates. The 1993 legislation also authorized a local citizen signature petition process to put the school year start date decision before voters instead of the local school board. The petition process authorized by the 1993 law was used in Sioux Falls in 2015, and 52% of city voters approved a school start date after Labor Day.
Voters in North Dakota revisited the topic in 2014 and rejected an initiative that would have required public school to start after Labor Day, 55.6% to 44.4%.
North Dakota was, along with South Dakota, the only state to feature a statewide ballot measure determining the state’s school start date. Forty states allow local school districts to decide school start dates or the start date is determined regionally. Michigan, Minnesota, and Virginia mandate that school starts after Labor Day statewide. The other seven states mandate that school cannot start earlier than a specific day in August.
In April 2019, Maryland legislators passed and then overturned a gubernatorial veto on Senate Bill 128 to allow local school boards to control school start dates. Previously, the first day of school had to be after Labor Day.
Background on legislative alteration:
South Dakota is one of 11 states (out of 21 with a process for initiated state statutes) that have no restrictions on how soon or with what majority state legislators can repeal or amend citizen initiatives.
From 2010 through 2018, 97 initiated state statutes and two initiated ordinances in D.C. were approved by voters. Of these 99 total initiatives from 2010 through 2018, 28 were legislatively altered as of April 2019. From 2010 through 2018, South Dakota voters approved five initiated state statutes. Of those, two—both 2016 initiatives—were legislatively altered.