Hundreds of California students could be sent home on the first day of school over a new vaccine law that took effect last month.

KPIX-TV reported Monday that parents are no longer allowed to cite personal or religious beliefs as a reason not to have their kids vaccinated. Kindergarten students and seventh graders must have proof that they received their immunizations.

For students in the Bay Area, Monday was the first day of school and Oakland school officials are prepared to turn students away from the classroom if they don’t have their vaccinations.

“There could be a few hundred kids that are not immunized and so we’ll be encouraging them as quickly as possible to get out there,” Oakland Unified School District John Sasaki told the station. “Their parents may try to drop them off and we’ll have to turn them away.”

Students who got their “personal belief exemptions” approved before January will be grandfathered into the new law, according to the station. The new law states they still must get their immunizations when they reach seventh grade.

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