A 17-year-old boy has been injured and five people arrested after going to Runshaw College armed with knives in what police are calling a targeted attack.
It follows a report to the Leyland college that a group of people were travelling there armed with weapons.
A group of males - several wearing balaclavas and face masks - showed up at the college as pupils were leaving for the day.
Several of the group were armed with knives and made threats towards pupils.
A 17-year-old boy, believed to be a pupil, was taken to Chorley and South Ribble Hospital with an arm injury.
A Lancashire Police spokesman said: "We were initially called at 10:40am this morning (Monday, March 4th) by a member of staff from Runshaw College after they had received an anonymous report stating that a group of people were going to attend the college with weapons by train from Manchester.
"Officers were deployed and whilst at the college at shortly before 4pm this afternoon, they have witnessed a group of males walking into the grounds whilst students were leaving. Some of the group were seen carrying knives and were making threats towards students."
As the incident unfolded, emergency protocols were in place with pupils kept on board buses.
A concerned mother who wished to remain anonymous said there was around ten police cars and five vans at the scene.
She heard people saying someone had been stabbed following a fight.
She added: "They wouldn’t let the buses go for ages and told driver to not let anyone else on the bus.
"It’s just so scary at the moment, you don’t know when the next knife attack will be. Obviously the police don’t want parents to panic but it is scary."
When police patrols arrived, the group made off from the college.
Three people who were inside a parked Nissan Micra close by were arrested. A fourth person who made off on foot was also arrested.
A Peugeot 306 has since been stopped on the M55 and a fifth person has now been arrested in connection with the incident.
Chief Inspector Gary Crowe from Leyland Police said: “We believe this was a targeted attack in that we think the group have gone to find someone and a separate student has received a minor injury. This was not a random attack.
“I would like to reassure people that the incident has now come to a close. The safety of the college’s students and staff remains our priority and so we have stepped up patrols in the area and this will continue. We have and will remain in close contact with the college.
“If you have any information, or any mobile phone footage of the incident, please make contact with us. You can call 101 quoting incident reference 933 of today (March 4th).”
Runshaw College principal Simon Partington said: "An incident took place outside the college's Leyland Campus this afternoon. The matter is being investigated by Lancashire police, and we understand that 4 people have been arrested for questioning.
"As a result of the incident today, the Leyland Neighbourhood Policing team will be continuing their investigations in the Langdale Road area tomorrow. If anyone has any information that might be of use to the police, please ring 101, quoting log number 0933."
The College added that it would be open at normal tomorrow.
It follows a emergency police stop and search authority being put in place at Leyland railway station for weapons.
It was put in place at 3.22pm and will remain until at least 10pm this evening. It follows information being provided to British Transport Police. Police officers are allowed to stop and search anyone without any grounds for suspicion.
A spokesman for the British Transport Police said: “A senior officer at British Transport Police has authorised the use of Section 60 Stop and Search Powers at Leyland station, the powers are in place until 10pm this evening.
"This authorisation follows intelligence in relation to potential violence and weapon enabled crime. Passengers and rail staff can expect to see an a number of highly visible patrols by BTP officers throughout the evening.
"If you have any concerns, or wish to report a crime, contact BTP by sending a text to 61016 or by calling 0800 40 50 40.”
Caroline Moon, ward councillor for Buckshaw and Worden on South Ribble Borough Council, said she was shocked by the reports.
She said: "This is the first I've heard of it until now. I will make contact with the police, that will be my first port of call.
"And as cabinet member for community safety I will check in with our chief executive.
"I will hope that everybody concerned is okay, that is the priority. Our role will be to support the police."
Councillor Moon, who is deputy leader of South Ribble Borough Council, said the council liaises regularly with Runshaw College.