Investigators are still evaluating the scene at an Atascadero elementary school, after threatening letters and a hazardous package were left on campus last week.
The school remains closed, forcing San Gabriel Elementary students to continue class at different campuses throughout the district.
District staff spent about 12 hours Sunday planning how to offer school to the nearly 600 students who could not return to San Gabriel's campus Monday.
Atascadero Unified School District Superintendent Tom Butler says they quickly prepared the three other campuses for the influx, including students and teachers.
Butler said in his 26 years working in education, he's never seen such a complex and unique situation.
"The normal routine of school has been so reassuring to students and staff," said Butler. "Keeping in the routines, keeping relationships that are positive, connected, keeping students with their friends, students with their teachers and other support staff, that's really what we've learned out of this-- these human connections that make it rich and also give us comfort."
Butler said, in addition food and transportation needs have also been met during this period.
Santa Rosa Academic Academy is hosting preschool and kindergarten classes, Santa Margarita Elementary has first through third graders, and San Benito Elementary has grades four through six.