Alarmed staff at Liberton High School called police who dispatched a team of officers to the scene amid reports of a ‘disturbance’.
The Evening News understand three teenagers from another area had made it as far as the school grounds.
But they were unable to get into the building itself.
It remained unclear why they were there, or who they were looking for.
Official said they were unable to go into further detail.
However Police Scotland said it had ordered further high visibility patrols to be maintained in the area to offer reassurance.
In a statement, they said: “Police received a report of a disturbance at Liberton High School at around 1.30pm on Monday 14th May.
“Officers attended and carried out inquiries and high visibility reassurance patrols during the afternoon.”
They added: “No-one was hurt during the disturbance and an investigation is ongoing.”
After news of the security scare began to spread among pupils and their families, the headteacher issued a text message to all parents.
It read: “There has been an incident at lunchtime involving 3 intruders. It is now in the hands of police.”
That sparked panicked rumours among worried parents, including claims a female pupil may have been slashed.
Both Police Scotland and City of Edinburgh Council moved quickly to reassure that was not the case, no-one had been hurt and that no weapons had been involved.
Education chiefs said police were taking the lead over the incident and they were working with detectives.
A City of Edinburgh Council spokesperson said: “We are helping Police Scotland with their ongoing inquiries into an incident at the school on Monday.”
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