Administrators at the Amarosa Academy, a small, alternative education school for grades 7 through 12, allegedly found a knife in a student's backpack and notified the police.
Officers arrived at 9:20 a.m. and met with administrators, who told them that it is school policy to check all student's backpacks before they enter the campus, police said.
An administrator checked the backpack of a 15-year-old student and allegedly discovered a "large hunting knife" in a sheath. Police said the knife was concealed in the plastic lining of a binder in the backpack.
The 15-year-old was arrested and booked on suspicion of felony possession of a dangerous weapon on campus, police said.
Santa Rosa police said it is unclear why the student allegedly brought a knife on campus.
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On March 1, 16-year-old Montgomery High School student Jayden Jess Pienta was fatally stabbed after an altercation in an art class and a 15-year-old has been charged with voluntary manslaughter in the death.
On Saturday, Santa Rosa Police Chief John Cregan said that his department has been called to schools in the city 945 times in the past year. Cregan would like to bring back the School Resource Officer Program, which was discontinued by the school board, he said.