Police received a report around 1:05 p.m. that there was a bomb-like object in the area of the school's front office, near the parking lot.
Pleasant Hill officers responded to the campus, located at 2097 Oak Park Blvd., along with the Walnut Creek Police Department's bomb squad, police said.
The school was evacuated, with students sent next door to the Oak Park Christian Center at 2073 Oak Park Blvd.
Ka'ae Boyd, administrative assistant at the church, said students had just been dismissed from school because of scheduled parent-teacher conferences when they were told to evacuate and go to the church shortly after 1 p.m.
By 2:30 p.m., the students had all been picked up by their parents, Boyd said.
Police and school officials said no injuries had been reported.