Youngsters at the school were shocked when the Year 6 pupil started showing off the knife to them in the playground.

He even waved it at one of them in a showy manner.

The younger children told their teacher, and the knife was confiscated. The boy, who has not been named, was excluded until the end of the school term for his behaviour following a meeting between his mother and headteacher Sarah Levy.

Peterborough City Council confirmed the action taken after Wednesday's incident was in line with local authority procedures.

Council spokesman Gareth Roberts said: "We can confirm a Year 6 pupil has been excluded until the end of term after admitting bringing a penknife into the school.

"The decision was taken following a meeting between the headteacher, the pupil and the pupil's mother and was in line with procedures.

"Both the school and Peterborough City Council take any incident involving a knife very seriously and, even though there was no suggestion the pupil took it into the school with any malicious intent, clearly this type of incident will not be tolerated.

"The city council will continue to liaise with the school and the pupil's parents."

He said the city council's procedures for dealing with this type of incident had been in place for a number of years.

The incident at the school in London Road, sparked concern among other parents who had children there.

A concerned parent, who did not wish to be named, said he first heard it from his son when he returned home that night.

He added: "I'm annoyed that the school didn't send a letter home with my son to explain what had happened. I went into the school and spoke to other parents about what had happened.

"Although no one was hurt, parents need to take more responsibility with their children, especially when it comes to something as dangerous as a knife."

The expulsion comes as the Government seeks to impose stricter punishments for those found carrying knives, following a spate of knife-related attacks in the London area.

Prime Minister Gordon Brown has announced that he wants to make it "unacceptable" to carry a knife, and anyone caught carrying one could face a severe community punishment or even jail.

So far this year, 21 teenagers have suffered a violent death after being the victims of knife attacks in London.