Archaeologists have found what they think is the remains of an Iron Age settlement under part of a Wearside school.
The surprising discovery was made by experts carrying out a study for contractors Balfour Beatty, who are working on the new 17.3m Northumbrian Water-sponsored academy to replace Castle View School.
The study is part of planning conditions laid down by Sunderland Council because school is on the site of the historic Hylton Dene, but archaeologist Dr Andy Towle said he did not expect to find Iron Age remains.
He said:"It was a surprise to be honest.
"The school was built in the 1960s so I would have thought anything here would have been destroyed in the construction.
"If anything, I thought perhaps we would have found medieval archaeology, but to have found probable Iron Age archaeology quite surprising."
Dr Towle said the archaeological evaluation had looked at three areas.
Two did not turn up any finds, but the third revealed a post-pit and ring-ditch, which would indicate an Iron Age roundhouse once stood on the site.
Groups of children from the school are now helping to sift through the site looking for artifacts and helping archaeologists to investigate.
"The kids are great," said Dr Towle. "They are full of enthusiasm. When you've been doing it year in year out you lose some of that, but seeing the kids being so enthusiastic reminds you of your own enthusiasm. It's been great fun."
Caroline McHale, director of business and community services at the school, said: "This is a fantastic opportunity for the children. It's an exciting discovery on their doorstep."
She added that it was great that the pupils had the chance to investigate the site for themselves before it disappeared forever under the new school.
Dr Towle said the site had been an interesting find, but the investigation would probably be wrapped up in the coming days.
Information gained from the dig will be sent to Balfour Beatty and the council for analysis, but work is likely to go ahead as expected.
"It's not like a motorway going through a monument," he said. "It's good because we are getting a little bit more knowledge and putting a bit of Iron Age on the map where there wasn't any before."
The new academy is due to open in September 2009.