Police responded to a “concern for safety” on the premises, a spokesperson for Surrey Police said.
The force arrived at Esher C of E High School at around 12.40pm on Monday.
Officers attending the scene were armed, the force confirmed.
Surrey Police said: “Uniformed armed officers at scene at Esher C of E High School following reports of a concern for safety.
“Enquiries being carried out inside and outside premises to establish circumstances.
“Students and staff at school remain inside building as precaution at this time. Further updates to follow.”
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