A judge could issue an injunction on Wednesday against Senate Bill 658, halting the new state law that bans mask mandates in schools.
A group of parents planning a rally in support of the injunction are at the Oklahoma County Courthouse.
Several parents said they are fighting the bill because they believe it has negative and possibly deadly consequences on their medically fragile children.
One protest organizer told News 9 that she also expects anti-vax/mask groups to be at the hearing.
Oklahoma is at the center of a federal civil rights investigation over the ban on school mask requirements.
State superintendent Joy Hofmeister said she was not surprised by the investigation.