Many classes at Rio Americano High School had fewer than half the normal number of students on Friday morning, despite a phone call and email from the principal attempting to reassure families that social media threats of school violence that circulated the previous night were not valid.

Nine teachers were also absent, at least some of whom called out after the principal’s message.

Posts circled on social media Thursday about apparent threats of violence against Rio Americano, Rosemont, Inderkum, Grant Union and Natomas high schools. But local law enforcement deemed the threats were not credible.

“We are closely monitoring the situation with the district’s Safe Schools team and want to reassure you that we have no evidence to suggest an actionable threat to our school community,” Rio principal Cliff Kelly said.

According to San Juan Unified, threats have been made against four district schools this week, but there is no evidence of any credibility to these threats.

“Our safety team is closely monitoring the situation in coordination with law enforcement,” the district said in a statement. “Each report is taken seriously and shared with the appropriate staff and authorities for investigation.”

They added that state and local law enforcement officials were aware and in communication with the district.

Despite assurances, students said they did not come to school out of an abundance of caution.

“Due to threats made against Rio and other schools in the area, I made the decision to stay at home today,” senior Katie Hickey said. “I don’t want to become yet another statistic, and I don’t want to fear for my life when I come to school. It is clear that something drastic needs to change to protect American students.”

The threats come a week after a Georgia high school shooting that killed four people.