Armed police swarmed outside the gates of a school amid "safety concerns".
Police confirmed they are in attendance at the scene, but would not go into any detail.
The school, has yet to comment as investigations into the incident continued.
SurreyLive said it was not known if classes were still in session or how many students remain on site.
A spokesman for Surrey Police said: "We are aware of and responding to reports of a concern for safety at Reigate School in Pendleton Road, Reigate."
They later followed their comment with a tweet which read: "Officers are at the location & carrying out further enquiries to establish the circumstances of the incident.
"We will provide further updates as & when we can."
The school is mixed for those aged 11 to 16 with academy status.
It is part of the Greensand Multi-Academy Trust.
Today is the last day of classes before half term next week.
The incident prompted speculation about what had happened at the school.
Thomas Gardiner tweeted: "What's going down near Reigate school??
"Received a text from school about police dealing with incident outside school.
"Son heard someone was stabbed, but hoping that's just a rumour!"
He also posted a video of around half a dozen police cars outside the school.
Parents are believed to have received a text message informing them of an incident outside of the school.
Another parent moved to allay parents fears saying: "Seems to have calmed down now, just picked up my boy from there."
Surrey Police confirmed pupils were sent home from the scene.
A spokesman said: “Officers are at the location and are carrying out further enquiries to establish the circumstances of the incident.
“We will provide further updates as and when we can.”
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