The message says there will be a mass shooting on May 9th on the campus.
The district says classes will be in session on that day.
"At this point in time all we have is the graffiti itself. There's no other information other than that. Should things change we would definitely change direction," said District spokesperson Elizabeth Graswich.
Parents are now trying to decide whether to send their kids to school on May 9th.
"I'm going to wait and find out exactly what goes on between now and May 9th, what kind of information that they say. But right now you want to be very cautious," said Ken Clifts.
Cindy James said she will send her kids to school.
"Because I think it is important for them to realize that we need to keep doing what we're doing and not let threats stop us from our lives," she said.
School district officials are praising the student who reported the graffiti and are asking any other students who know something about this threat to come forward.
"We have an anonymous tip line that we set up in the Fall and we have gotten an amazing number of tips. Students are coming forward with lots of information and we appreciate it because we follow up on every single one of them and are able to take action," Graswich said.
San Ramon Police said they haven't made any arrests and don't have any leads. They will keep extra officers at the school through May 9th.
San Ramon Police are making sure to have a visible presence at Cal High School today after a threat of a mass shooting was written on the bathroom wall. pic.twitter.com/GxUv25eR53— Amy Hollyfield (@amyhollyfield) May 2, 2019