Demonstrators rallied outside the state capitol in Sacramento Wednesday morning in support of Senate Bill 673, before the state senate's education committee voted down the measure.
Backers say the bill would have allowed parents to thoroughly review what their children are being taught about sex education in the state's public elementary schools.
"I'd like to inform myself a little bit more in what exactly in detail, what they're going to be hearing in school," said Desert Hot Springs parent Monica Rodriguez.
The legislation sponsored by Senator Mike Morrell, a Republican from Rancho Cucamonga, would also have required parents of students grades K through 6 to sign permission slips before children participate in sex ed classes.
The vote to kill the measure in the senate education committee was along party lines 5 to 2.
"My friends across the aisle voted it all down. Apparently they want to cut parents out of the loop. They say it is unnecessary to post everything. Kind of amazing to me," said Morrell.
Opponents of the bill included the California Women's Law Center.
They argued it would change sex ed for elementary school students from an opt-out to an onerous opt-in process.
Teacher's unions also opposed, including the California Federation of Teachers.
"We believe that school districts should have the flexibility to provide instruction appropriate for their students, and that the current law provides parents the opportunity to opt out of sexual health instruction should they choose to do so," said Matthew Hardy, Communications Director for the California Federation of Teachers.
A number of parent protests and demonstrations have happened in school districts around the state over the past few years after districts adopted new sex ed training materials to comply with the California Healthy Youth Act, which state lawmakers passed in 2016.
Some parents claim the material is "too much too soon" for children.
47 thousand people signed an online petition in support of SB 673.
Morrell says he will continue to promote legislation aimed at "giving parents more control over how their children are taught about sex education" in public schools.