Lake Tahoe Unified School District Superintendent James Tarwater ordered all schools in the district on yellow alert after the shooting at a Connecticut elementary school left 20 children dead.
Schools were requested to secure all perimeter entrances and monitor school grounds at noon Friday as a precautionary measure against the possibility of a copycat act.
Staff members were asked to be vigilant and administrators and security personnel increased surveillance at the schools, according to a LTUSD statement.
Each of the schools hung the flags at half mast to honor the victims.
"When tragedy strikes, the results are traumatic, both for those directly affected and for the community of people who know them or identify with them. But when something like this happens at a school, to very young children, it hits closer to home and we may feel helpless," LTUSD spokeswoman Angie Keil wrote in an email.