Oakland Unified School District spokesman Troy Flint said officials are restricting access to Peralta Elementary School at 460 63rd St. because someone has "a vendetta" against the student's family and has made "a vague threat to do harm" to the family.
Flint said a suspect sent two notes to the student's mother and that the second note alarmed school officials because the person indicated that they know where the mother's child goes to school.
Police in both Oakland and San Francisco have been notified about the threat because the family lives in Oakland and the mother works in San Francisco, which is where she received the written threats, according to Flint.
He said school officials are slowing students and family members down as they come to Peralta today and are only allowing people to use one gate at the school, which normally allows people to use multiple gates.
Flint said a police officer is on duty at the school and parents and family members are only being allowed to pick up students at limited times.
"There's been no definitive threat but we're taking precautions," he said.
Flint said school officials will confer with police about whether to only employ the precautions today or to continue them next week.