Just like how here they tend to slide in major ballot initiatives raising taxes or doing other things desired by the Left on off-year primary ballots, where most Republican races aren’t contested, and thus few Republicans bother to show up at the polls.
In 2012 I voted on the same local school issue 3 times in a period of about 3 months. The first 2 times were on the same day as state and presidential primaries and it failed and the 3rd time it was a single issue ballot on a random weekday a couple weeks before the general election and it passed.
The law has since been tightened and school votes have to take place on specific days.