The incident happened at Tewkesbury Academy in Ashchurch Road which was put under lockdown.

Gloucestershire Police said officers were called at about 9.10am on Monday to reports a pupil had stabbed a teacher - with a teenage boy later arrested.

Sky News correspondent Dan Whitehead spoke to Sarah Penny whose daughter Issy was inside the school.

"Mum I'm really scared," the 13-year-old messaged.

"They had guns, they had armed police."

In a statement to the parents and carers of pupils, headteacher Kathleen McGillycuddy said: "We appreciate that this morning has been a worrying time for all associated with Tewkesbury Academy."

She added: "We were alerted shortly before 9am this morning to reports of a serious incident which left a male member of staff in need of hospital treatment.

"The school was locked down and police were called immediately when we became aware of this incident."

Downing Street said Prime Minister Rishi Sunak's thoughts are with those impacted by the incident.

A crowd of about 100 people gathered outside the school after the stabbing and uniformed officers stood on duty at its entrances.

Earlier on Monday, teachers at the nearby Tirlebrook Primary School posted on Facebook to say their school had also been locked down on police advice and urged parents not to attend.

"An incident has occurred this morning at Tewkesbury Academy and we have been advised by Tewkesbury Police to put in place a lock down," they said.

"We have a police presence at school and are being fully supported at this time. We would like to reassure all families that children at Tirlebrook and Little Oaks are safe and well.

"We must ask that families do not come to school during this time as this could compromise the police operation currently underway and also compromise the safety of the children.

"During this situation all school staff will be supporting the children and liaising with the police so we would ask that you do not attempt to communicate with the school office.

"We thank you all for your support and will update you as soon as possible when we know more."

Education Secretary Gillian Keegan said: "I am deeply concerned by reports of a stabbing at Tewkesbury School.

"We are closely monitoring the situation and remain hugely grateful to the emergency services who are currently on the scene.

"My department is on hand to support the school as the situation unfolds."

A spokesman for Tewkesbury Academy said it would be following police guidance on how pupils will be allowed to be sent home following the lockdown.

He said: "No decision has yet been made on when the school will reopen, but we will be drawing up plans to support our students and staff in the wake of this incident.

"We are grateful to all our staff, parents and students for their patience and understanding during what has been a difficult morning, while our thoughts are with our injured colleague - we wish him a swift and successful recovery."

The prime minister's official spokesman said: "It is a live investigation, but the prime minister's thoughts are with the individual who has been injured and with the staff and pupils of the school who would obviously be extremely concerned.

"He wants to thank the police and emergency services for their ongoing response."