By Angela Harrison BBC News education reporter

More than one million people were killed at Auschwitz

Twenty-three UK students have joined Holocaust survivors and world leaders at a memorial service at Auschwitz concentration camp in Poland.

The group, from Ounsdale High School in Wombourne, Staffs, were "profoundly affected" by what they saw and heard.

In snow and sub-zero temperatures, they heard the harrowing testimony of survivors and statesmen speaking of the need to fight fascism.

More than one million people - mainly Jews - were killed by the Nazis there.

More than six million Jews were killed in the Holocaust.

The children made the visit through a project called Their Past Your Future.

Group leader Dan Phillips, speaking at Auschwitz, said the experience had been "profound" and "sombre".

"Everyone has been saying how much of an impact it has been for them to visit an actual site," he told BBC News.

"Until you come here, what you have is statistics and facts, but when you are here it all comes crashing in on you.

"There is no hiding from the scale of it, from the reality."

'Truly chilling'

As they walked around some of the buildings in Auschwitz where prisoners had been held, the group met a woman who had survived the camp.

Student Claire Portic, 16, said the meeting had affected them greatly.

"She told us how she had survived and it was very moving to hear her story.

"We asked her if she had written about what happened but she said she didn't know how to put it into words and that she didn't want to because that would make it real."

The sixth-formers were clearly disturbed by the images and exhibits in the museum at the camp.

"It was truly chilling," said Claire Johnson, 16, "seeing suitcases with children's names in, their clothes and the millions of shoes, all different sizes.

"It was incredibly moving.

"I almost felt guilty."

How could anyone do that? Claire Portic, 16

The sixth-former said the camp would haunt her. She had dreamt the previous night that she was a prisoner there.

Claire Portic said the sight of torture chambers had made her feel horror and disbelief.

"How could anyone do that?"

The visit had been very disturbing but she was pleased to have gone.

"If I had not, I would not have understood what happened, no matter how many books I might have read or programmes I might have seen."

Two-thirds of all Europe's Jews were murdered in the Holocaust, along with Roma, Poles and other Slavs, Soviet prisoners of war, homosexuals, and mentally and physically disabled people.

'Ongoing problem

During their six-day trip to Poland the 23 students also also visiting the site of the labour camp at Monowice.

They saw the UK Minister for Veterans, Ivor Caplin, unveil a plaque recording the names and regiments of the 38 British prisoners of war who died there.

The teenagers are going to camps at Belzec and Majdanek and towns whose Jewish populations were killed during the Holocaust.

Mr Phillips said: "Some of the more out-of-the-way places we are visiting still have a large amount of anti-Semitism.

"The trip is not just about the past, but about what is an ongoing problem.

"The students are visiting places where most people do not go. Hopefully it will put some perspective on one of the worst outrages in history."

The Their Past, Your Future project is funded by the Imperial War Museum and the Big Lottery Fund.