All the schools in the Lake Tahoe Unified School District will go on "yellow alert" Friday as a precautionary measure against doomsday violence, according to LTUSD spokeswoman Angie Keil.
Schools will secure all perimeter entrances and monitor school grounds, and staff will be asked to be extra vigilant. There will also be additional police stationed at South Tahoe Middle School and South Tahoe High School.
Keil said rumors of violence against the schools have circulated partly because of an interpretation of the Mayan calendar that predicts the world will end Friday.
"We take these threats seriously. It's not funny to make them," Keil said.
More than 30 schools in Michigan closed early for the holidays because of rumors connected with the Mayan prediction that add to fears raised by the shooting in Connecticut last week.