More than 100 pupils staged a strike to protest about mounting knife violence.

Patcham High pupils refused to go into lessons and instead filed on to the playing field. The demonstration, which lasted an hour, followed an alleged knife attack on a pupil outside the school yesterday.

It is believed one pupil held a craft knife to another pupil's throat outside the school grounds on Tuesday afternoon.

It is not yet known whether the knife was taken from one of the classrooms.

Pupils said they no longer felt safe and wanted more CCTV cameras and a higher staff presence at break times.

They began the protest at 9am and sent representatives to talk to headteacher Paula Sargent about their concerns before returning to lessons about an hour later.

Mrs Sargent said: "No one was stabbed although there are allegations of a knife being involved."

"I fully understand parents' concerns but when the children are in school they are safe.

"I can guarantee their safety in school but I cannot do that if, as in this instance, they leave the grounds."

Mrs Sargent said the protest began before tutors were able to speak to pupils about the attack.

She said: "We had no time to talk to them properly and reassure them before they started the protest."

The school monitors the number of knives used by pupils and is investigating whether one is missing.

A Sussex Police spokeswoman confirmed officers were investigating a possible assault involving two pupils from the school but would not give further details.