OLYMPIA, Wash. — Voters have approved Referendum 90 mandating sex education in Washington’s public schools.

The vote allows Democrats’ wide-ranging mandate for public schools to stand and take effect later this school year.

It’s the first time in the nation that a sex ed bill appeared on the ballot.

Under the law, schools must teach sex education beginning in kindergarten, but they can design their own curriculum and parents can opt their children out of the lessons.

Nearly 60% in Tuesday’s count were favoring Referendum 90.

Opponents of the measure argued that mandating such lessons strips power from local school boards, while objecting to certain sex ed topics.