A 15-year-old boy who was fatally stabbed at a school in Sheffield has been described as a “lovely lad” and the “life of a party”.

Floral tributes and messages have been left outside All Saints Catholic High School, where the boy, named locally as Harvey Willgoose, was injured.

A boy, 15, has been arrested on suspicion of murder and remains in police custody, South Yorkshire Police said.

The force said it was working “at pace” to build a full picture of what had happened.

One message left outside All Saints described the teenager as someone who had been “the life of a party” and who had “brought joy and laughter to everyone who knew him”.

His “bubbly personality was contagious”, it added.

“I’ll never forget all the moments, all the laughs. You’ll be missed by so many,” it said.

A teenager who said he had known the 15-year-old also left a bunch of flowers outside the school.

The 17-year-old, who studies at a local college, heard the news through friends and said the boy who died had been a fan of Sheffield United.

He said: “I’m a bit upset to be honest, it came as such a shock.

“He seemed quite a happy guy and a nice guy to be around.”

One All Saints pupil said the victim had been a “lovely lad”.

“He would make your day better hearing him down that hallway. You didn’t have to personally know him to be upset,” the 17-year-old said.

“Teachers loved him, students loved him, everyone loved him.

“I’ve been at the school for seven years now and nothing like this has ever, ever happened.”

On Monday a number of parents arrived at the school to collect their children early.

One told the BBC they were keen to get their youngster home after hearing a variety of rumours about what had happened, adding the “kids were getting panicked”.

According to the local newspaper The Star, the school’s head teacher sent a message to parents on Monday.

He said it was with “shock and sorrow” that he had to tell people a pupil had been fatally stabbed.

He also said the school would be closed on Tuesday.

Assistant Chief Constable Lindsey Butterfield said her force was working to establish “how this tragedy unfolded” and used a news conference to urge people to “be mindful that there are loved ones at the centre of this”.

All Saints head teacher Sean Pender had sent a message to parents last Wednesday about a lockdown at the site which he said was due to “threatening behaviour between a small number of students”.

Asked during the news conference about the reports, ACC Butterfield said she could not share any information relating to it.

But she urged people to avoid speculation and sharing content online “which could be distressing to them [the family] and detrimental” to the investigation.

Asked about the incident while on a trip to Brussels, Prime Minister Sir Keir Starmer said his first thoughts “as a father” were with the victim’s family.

“The terrible stabbing in Sheffield is one where I think the whole country would want to reach out to the family, to the friends, to the school, the entire community in their grief and mourn with them,” he said.

Louise Haigh, the MP for Sheffield Heeley, said the news was “horrific” and that “serious questions” would have to be answered about how it could have happened.

Anti-knife crime campaigners in the area have said incidents like this should not happen.

Amaan Ahmed, who manages the Castle Asian Community Trust near the school, said he feared the boy’s death would leave parents wondering if they should send their children back to school.

“If it can happen in a public place like a school, people will be worried about going to the park I think too,” he added.

Sheffield-based Anthony Olaseinde, who works for the charity Always an Alternative, said the incident was “heart-breaking”.

“Something like this should not happen,” he said.

He said the charity had held sessions at All Saints and worked with young people at the school.

Reverend Steve Chalke MBE, the founder of Oasis Academy schools chain, said knife crime was a symptom of wider problems.

“The issue is lack of inclusion, the issue is mental health, the issue is poverty, the issue is grooming, the issue is exploitation on huge council housing estates, the issue is exclusion from school.

“We need to do more to include kids. You can’t defeat knife crime, you got to double up on inclusion.”

Knife crime campaigner Alison Cope, whose son Joshua Ribera was stabbed to death in a street in 2013, said knife crime happened in schools on “rare occasions”.

She said: “I see social media fuelling so many arguments in school and some of those arguments are turning into real life.

“We have seen young people murdered because it started as an argument on social media.”

If you are affected by any of the issues raised, help and support is available via BBC Action Line.