A group called "Privacy for All Students" is challenging the new California law that gives transgender students a long list of rights.
They've collected 620,000 signatures to get the initiative on the ballot next November. At least 505,000 valid signatures are needed.
Gov. Jerry Brown signed the bill into law in September, making California the first state to give new rights to transgender students in elementary and high school.
Those rights include being able to choose to play on boys' or girls' sports teams, as well as being able to use boys' or girls' bathrooms and locker rooms.
Opponents say the law violates the privacy of other students.