Hundreds of youngsters were locked in their classrooms by teachers after a knifeman walked unchallenged into a West Midlands school yesterday.

The man and an accomplice got into Uplands Manor Primary School in Smethwick, Sandwell, through an unlocked gate just before the end of infants' lunchbreak at 1.50pm.

Teachers rang the school bell to bring the baffled four to seven-year olds inside, locked all doors and rang police. The knifeman was arrested by four officers and taken to a secure mental health unit to be assessed.

His accomplice is believed to have been released.

No one was injured but Collette Sheridan, a dinner lady at Uplands whose five-year-old daughter Sheridan Bains (pictured) is a pupil there and was playing metres from the knifeman, said they had feared the worst.

"They were only inches from tiny children who were running around them. The pupils didn't know what was happening, it was all very quiet," said the 28-year-old mother- of- three, from Smethwick.

"I told a teacher I was going home and she said 'no, you can't. One of those men in the playground has a knife'.

"The teachers told the children there were 'naughty men' outside."

She said when police arrived and took off one of the men's coats, they "found a massive knife".

"It was silver and must have been more than a foot long," she said.

"I just couldn't believe what I was seeing. Myself, my child and hundreds of others could have been killed. I feel sick as a dog thinking about it."

She said parents had previously raised the issue of security at the school and unless its gates were bolted and locked at all times from now on, she would take her daughter and son, Aaron, aged nine, out of the school.

A West Midlands Police spokesman said a 22-year-old man was detained in connection with the incident.

The latest incident has again highlighted the issue of school security.

In November, two youngsters at The Oratory Roman Catholic Primary School in Oliver Road, Edgbaston, Birmingham, were injured after staff foiled a thief thought to have been armed with a knife.

And in 1996, paranoid schizophrenic Horrett Campbell went berserk and attacked nursery nurse Lisa Potts and 18 children with a machete at a Wolverhampton nursery.

He was detained indefinitely at a psychiatric hospital.