Los Angeles Unified School District (LAUSD) officials canceled classes Tuesday after receiving an email threat from overseas, warning of an attack with assault weapons and explosives.
Superintendent Ramon Cortines says the San Bernardino attack along with heightened security concerns contributed to the closure.
VIDEO: LA schools deemed safe after threat investigation
"I as superintendent am not going to take the chance with the life of a student," Cortines said.
Police in San Francisco began patrolling schools, while other school districts went into alert mode.
"What we did was we increased the presence in and around our schools here in San Francisco," said San Francisco police Officer Albie Esparza.
Most schools in San Francisco have a school resource officer. With the threat in Los Angeles, those officers in San Francisco were given priority status.
"In case anyone does call the police from a school, or any type of campus, we would have a top priority response," Esparza.
VIDEO: New York receives similar threats to LA, calls it a hoax
There was never a threat of violence to schools in San Francisco, still it was a chance to review their safety plan.
"All of our principals were reminded of procedures if they receive a bomb threat. We do regular safety drills. We have crisis response teams going over their specific roles at all of our schools," said Gentle Blythe of the San Francisco Unified School District.
Oakland Unified School District has its own police force. Chief Jeff Godown was in contact with the superintendent.
"You take every threat seriously," Godown said.
Godown is a veteran of the San Francisco and Los Angeles police Departments. He believes the San Bernardino shootings influenced the school district's decision to close.
"I'm sure it had something to do with that. What I heard was the FBI had said that was not a viable threat but he still made that decision and you have to stand by his decision," Godown said.
His former boss in Los Angeles William Bratton now leads the police department in New York City. Bratton believes Los Angeles Unified overreacted.