Holyrood Academy, Chard went into lockdown on Tuesday, 13th November when the head teacher was informed of a possible intruder.
The Avon and Somerset police was called in, and they arrested a teenager on affray.
A spokesman said: “We were called to reports of a disturbance in Chard at around 12.30pm.
“We arrested a teenager on suspicion of affray and seized what appears to be a metal bar.”
After that, an email was sent to parents informing them about the lockdown procedure. It said that the students and teachers had been of impeccable behaviour at the time.
Matthew Collins, the head teacher of the south Somerset school, later released a statement on the school’s website saying, “At 12.20pm today (13.11.18), I was informed by a credible source that there was a risk of an intruder intending to access the Holyrood Academy site.
“We immediately contacted the police and our lockdown procedure was initiated.
“The police were able to apprehend and detain the suspect before they reached the Academy site.
“The lockdown was in operation for no more than 15 minutes, after which the school day returned to normal.”