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Editor’s Note: A follow-up story has been published.
Menlo-Atherton High School was placed on a “secure campus” order Wednesday after Atherton police received a tip about a potential threat involving a former student.
The tip, reported Sept. 10 through Menlo-Atherton’s See Something, Say Something tip line, indicated the former Menlo-Atherton student, who is now enrolled at another area school, had posted concerning content online referencing Menlo-Atherton, police said.
Officers were immediately deployed to multiple locations on campus to ensure the safety of students and staff. Laurel School, lower campus, and Encinal School — which are located nearby — were also placed on secure campus status as a precaution.
The San Mateo County Office of Education’s “The Big Five” protocol, which Menlo-Atherton uses, that during a secure campus order, staff and students must remain inside classrooms and that all doors are closed and locked. School instruction can typically continue during the order.
Menlo-Atherton’s secure campus order began around 12:55 p.m. and lasted approximately one hour. Student journalists at the school said that Menlo-Atherton Principal Karl Losekoot told the school over the announcement system that students could be escorted to the restrooms starting at 1:27 p.m. but the order did not officially end until 1:59 p.m. The order was lifted once the student was located. Losekoot said in an email to parents that the school made the decision to issue a secure campus order.
Atherton police, working with school staff and other law enforcement agencies, located and detained the former student. Investigators said there is no ongoing threat to the school community.
There was never an active threat or dangerous situation at Menlo-Atherton, Losekoot said in his email
“The Atherton Police Department is grateful for the swift actions of our officers, school staff, and partner agencies in ensuring the safety of the Menlo-Atherton and Laurel school communities,” the police department said in a statement.
“The secure campus on September 10, 2025 at Laurel Lower Campus and Encinal School was prompted by a threat to nearby Menlo Atherton High School as that school went into secure campus. Due to our two campuses’ proximity to MAHS, and in communication with Atherton Police Department, our schools entered secure campus around 1:00 p.m. and were cleared when the threat to MAHS was resolved, again in communication with APD, at about 2:00 p.m,” Menlo Park City School District Spokesperson Parke Treadway said in a statement.
“MPCSD students were not threatened or endangered; secure campus was initiated out of an abundance of caution… We are grateful for the strong partnership with our police departments,” Treadway added. She also said after-school pickup was able to proceed as normal.
Another Sequoia Union High School District School, Carlmont High School in Belmont was placed on a secure campus order earlier in the day that ended at 1:15 p.m.
“Carlmont High School was placed in Secure Campus at the request of the Belmont Police Department due to reports of a potential threat in the neighborhood… All staff and students are safe,” Sequoia Union High School District Spokesperson Naomi Hunter said.
The Belmont Police Department declined to comment. It is not clear if the secure campus orders are related.
The investigation remains active, and police encouraged the public to continue reporting suspicious activity.
In 2022, two students brought guns to Menlo-Atherton’s campus in separate incidents. The school said it did not believe either posed a threat to students or staff.
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