Los Angeles Police Chief Charlie Beck said Monday that an officer will stop each day at the city's 600 public elementary and middle schools when classes resume after the holiday break.
In addition, Los Angeles Unified School District Superintendent John Deasy said three school police officers were traveling to Connecticut to offer their help and learn about the tragedy.
"It will be very emotional for the entire LAUSD community ... when classes resume," Deasy wrote in a statement. "Then, as now, our thoughts and prayers will be with the people of Newtown."
Police departments around the nation acted quickly during the weekend to arrest several people suspected of posting alarming threats online about the rampage.
In Los Angeles, police booked Kyle Bangayan, 24, of Pomona for investigation of making criminal threats against elementary schools in a Facebook posting. However, the district attorney's office later decided against filing charges, saying Bangayan made no specific threat to a person or school.
Other arrests were made in Ohio, Tennessee and Fairfield, Calif., where authorities arrested a man on Monday suspected of praising the Connecticut attack on his Facebook page and saying he had been thinking
Police departments and school districts statewide were reassessing their security procedures as many students were off for the holidays.
Tom Torlakson, state Superintendent of Public Schools, joined the California Emergency Management Agency in sending a joint message to all school districts asking them to take another close look at their safety plans and prepare for a worst-case scenario.
Officials at Sacramento City Unified will meet with law enforcement authorities later this week, although the district has no plans for additional security on campus, said district spokesman Gabe Ross.
"I think it's a fine line between making sure we have heightened awareness and making sure they have whatever support and resources they need, and making sure the kids have as much normalcy as possible," he said.
In San Diego, police officers were ordered to visit schools while on routine patrol.
The department will also link dashboard computers in squad cars to campus security cameras using wireless connections as part of a long-running effort to give officers a look at unfolding crimes, Chief William Lansdowne said.
San Francisco Unified School District asked all of its campuses to reassess emergency plans for everything from shootings to earthquakes, said school Superintendent Richard Carranza.
The district wasn't planning any specific events related to the Connecticut shooting, but it was still a prominent topic among teachers, said Kit Bell, a second-grade teacher at Sunnyside Elementary in San Francisco.
"We're all devastated. We're all asking the same questions. What would we have done? What could we have done?" said the 65-year-old mother and grandmother.
Associated Press Writers Gillian Flaccus in Orange County; Don Thompson in Sacramento; Elliot Spagat in San Diego and Terence Chea in San Francisco contributed to this report.