A proposed ballot initiative in California could set up a big fight between the state’s powerful teachers unions and education reformers.

According to the Wall Street Journal, the proposed measure would add language to the California constitution a guaranteeing all students a quality education. That’s where the conflict with unions begins because it:

…could allow [reformers] to use the courts to challenge teacher tenure laws and other policies they believe are harming public school students.

Similar ballot measures were proposed last year in Minnesota and earlier this year in New Mexico. As with the California proposal, they would put children’s right to a quality public education in state constitutions.

The stakes are particularly high in California, America’s most populous state and home to some of the nation’s most powerful teachers unions, which have previously opposed efforts to weaken tenure and other protections for their members.

Which means if the measure does make the ballot, a very rough, very expensive campaign will follow.

But first, backers will need to collect more than a million valid signatures from registered voters. It will be a big issue to watch.