Thousands of pupils across the UK have been forced to evacuate their schools amid a series of bomb scares from callers threatening to “take children’s head off”.

At least 21 schools have now admitted to receiving "panic inducing" warnings from an anonymous caller warning of a bomb on site – leaving teachers no choice but to pull students out of classrooms during GCSE examinations.

Canterbury Academy in Kent said it received a message saying that “the shrapnel will take children’s heads off”. Police were called to the site but were unable to find anything suspicious, causing many to believe the calls were a hoax.

According to Kent Police, Barming Primary school in Maidstone was also closed this morning after an “anonymous phone call”.

Two schools in Peterborough were also evacuated and a road was closed following a bomb threat.

Voyager Academy and Discovery Primary School were cordoned off by police.

One student said: Why put a bomb in discovery with children like it makes no sense.

“That really scared me I literally thought a bomb was going to blow up in front of us.”

Canterbury Academy head teacher Phil Karnavas said: “It's almost certainly a hoax but with what's happening across Europe I'm not prepared to take that gamble.”

He added that secretarial staff received “repeated” calls from an adult male claiming an explosive device was hidden in the school.

Police confirmed that an anonymous call was made at 10.13am and that the school was evacuated as a precaution.

The Cambridge News website reported a suspected hoax bomb threat at Mayfield Primary school, and Emsworth Primary School in Surrey has been evacuated with staff and children moved to a neighbouring school as police probe a bomb threat.

Emsworth headteacher Kate Fripp told local news website UKNIP: “There has been a security incident at Emsworth Primary School today.

“All children are safe and are at Glenwood School receiving refreshments.

“The police are on the school site and we expect to be allowed back in within the hour.”

Whiteley Primary and Kingsham Primary schools, also in Peterborough ,have issued security alerts, according to the website.

Children were sent home from Wootton Upper School in Bedfordshire, police said.

Meanwhile Oulder Hill School and Redwood School in Rochdale were evacuated after calls warning of a “suspicious package“.

Greater Manchester Police say they were called this morning and are still on the scene.

• Canterbury Academy, Kent

• Barming Primary School, Maidstone

• Voyager Academy, Peterborough

• Discover Primary School, Peterborough

• Wootton Upper School, Bedfordshire

• Redwood School, Rochdale

• Oulder Hill School, Rochdale

• Emsworth Primary School, Hampshire

• Kingsham Primary School, Chichester

• Whiteley Primary School, Fareham

• Rosebrook Primary School, Stockton

• Cranmere Primary School, Surrey

• Mayfield Primary School, Cambridge

• Blacon High School, Cheshire

• Crabtree Farm Primary School, Nottingham

• Lindisfarne Middle School, Northumberland

• Charville Primary School, Middlesex

• Dafen Community Primary School, Llanelli

• Pinhoe Primary School, Essex

• Middleton Primary School, Leeds

• Lindisfarne Middle School, Northumberland