Gov. Jerry Brown signed SB 48 earlier this month, requiring that students be taught about the contributions made by lesbian, gay, bisexual, and transgender Americans in their social studies classes.
But a coalition of conservative groups has filed referendum papers to repeal the bill.
"When you start talking about changing history textbooks to please a special interest group, that's what really raised people's hackles, that's what we've been hearing," Pacific Justice Institute spokesperson Matthew McReynolds said.
When he signed SB48, Brown said, "history should be honest."
The 'Stop SB48' coalition has 90 days to gather 500,000 valid signatures to qualify the measure for next June's ballot.