School officials discovered the noose Friday, though no evidence was found pointing to a specific target, police Lt. Paul Doroshov said Tuesday.
"We're taking it seriously," he said. "We're not discounting anything."
Local activist Dr. Jann Murray-Garcia said she has called for a community meeting about the incident, which she said could be inspired by racism, the Sacramento (Calif.) Bee reported Wednesday.
"A single noose -- it's a symbol of terror," she said. "We don't want to wake up to a symbol of hate in a place that belongs to the entire community."
Winfred B. Roberson Jr., superintendent of the Davis Joint Unified School District, said in a statement the incident stems from fear and ignorance.
"This isolated event does not distract us from the positive work and cultural responsiveness … in (the district) and the city of Davis," he said.