A pupil who allegedly assaulted a teacher at a school in Milford Haven has been charged with inflicting grievous bodily harm and possession of a bladed article on education premises.

Dyfed-Powys police said the 15-year-old boy had been remanded in custody and was scheduled to appear at Swansea magistrates court on Saturday. The senior investigating officer, DCI Matthew Briggs, said: “We are continuing to support the victim whilst they recover from this traumatic event.

“Following detailed inquiries by specialist officers, injuries initially assessed and described as non-stab injuries have now been confirmed as stab wounds. A statement at an early stage of the investigation was based on preliminary information available at the time.

“There will continue to be a higher than usual police presence in the area over the coming days to provide further reassurance. Officers will be working closely with local secondary schools to offer support over the coming week”.

The incident took place at Milford Haven comprehensive school in the Pembrokeshire region of south-west Wales on Thursday after a report that a teacher had been assaulted by a pupil brandishing a weapon.

The teacher was taken to hospital for treatment and later discharged, police said. The school was closed on Friday and police said all of the pupils “returned home unharmed”.

After the incident, the Welsh first minister said “violence of any kind has no place in our schools”.

Eluned Morgan visited the school only last week and, on Thursday evening, said in a statement shared on social media: “I am deeply concerned by the incident at the school in Milford Haven. Having visited the school only last week, this news is particularly shocking.

“My thoughts are with the injured teacher, their family and the entire school community during this difficult time.

“I want to pay tribute to the emergency services and school staff for their swift and professional response in ensuring the safety of pupils and staff.

“While this remains an active police investigation that must be allowed to proceed without interference, I want to be unequivocal … violence of any kind has no place in our schools.”

She added: “The Welsh government will continue to work closely with local authorities, schools and partners to support all those affected and to ensure our schools remain safe environments for learning and care.”

Neil Butler, the NASUWT union’s national official for Wales, described the incident as “frightening”.

He said in a statement: “Teachers sign up to become stewards of the next generation, and to share their joy and passion for education.

“We must remember that, like everyone else, they are entitled to be safe at work.

“We wish the injured teacher a full and swift recovery. But it may not be that simple. As violence in schools increases, teachers will need more than hopes and prayers.”