Students had to be sent to an emergency van to be cleaned when suspected asbestos dust fell on them from their school building.
The extent of the problems at Hetton School's old site was laid bare before the House of Commons as its acting headteacher and its former headteacher told its Public Accounts Committee about the problems they faced while waiting for it to be rebuilt.
The plans to rebuild the school - one of several which were proposed across Wearside and East Durham because they were in such a bad state of repair - was hit by a delay following the collapse of the deal that was meant to financially back the project.
The project was finally complete in September.
Acting headteacher Craig Knowles and former headteacher Phil Keay presented evidence to MPs as the meeting looked at capital spending for schools and scrutinised the Department for Education and Education Funding Agency on whether they delivered effectively on buildings.
The appearance by the school's leaders was organised by Houghton and Sunderland South MP Bridget Phillipson, who sits on the committee.
The session heard how the old school's state led it to being shut on several occasions and a series of safety measures being drafted in to keep children safe while waiting for the project to begin.
The committee was told that while asbestos was largely concealed within the building, windy weather would cause tiles to move and dust to fall.
The school representatives said this meant time was lost in the classroom for children when it had to be closed because of structural problems, as well as times when its heating system was not working.
Mr Keay said: "Some ceiling tiles were taped together so therefore should have been secure, but on windy days wind would get through the building and through open doors and the ceilings would lift.
"We had two or three cases we had to close off the school and students had to in fact had to go into the de-fumigation van, an emergency van, to make sure they were de-dusted and hosed down and cleaned, and it really was that serious.
"Obviously parents were informed, the emergency services and so on, but it was not a building that was fit to have children in it for several years really, prior to its closure and us moving to the new building."
Mr Knowles spoke of how in September, the school moved into its new building.
He said: "The impact on the students is that they can now actually go about their learning with a mental readiness that previously wasn't the case.
"Perhaps before, when they would have had to come in from the rain and keep their coats on because of the lack of heating, and have those kind of issues, where they were just trying to go about their work to learn, they're not there any more.
"We do have a good new building, it's not without its continuing issues, but all those issues that I've mentioned they're not there any more.
"It's a fantastic environment for young people to go about their work, to progress, to achieve and it's great for the staff was well, because they can have confidence in their preparation and what they are trying to achieve."
After the meeting, and via the school's website, Mr Knowles said it had been a "great opportunity" to speak to MPs and members of the department and the agency.
He added: "As a school we have a fantastic building that , although not without its faults, is a great environment for students and staff to develop in.
"However, we have had unforeseen costs this year that we believe should have formed part of contingency within the EFA budget and have now fallen on the school.
"These costs have to be found from our depleted revenue budget and therefore means we have less to spend on our real priorities of high quality teachers in every classroom, supported by high quality non-teaching staff.
"Despite these difficulties we have a clear plan for the school’s future that will allow us to continue to prosper as a good school.”
Mr Knowles added: “One thing for sure, the future is bright at Hetton School, because we prioritise the most important thing – putting our students first”
The committee also heard £7billion is needed to bring the country's school sites up to a decent standard and that amount again to make them a "good standard."
There is also an issue over the demand for school places, with 420,000 more places needed by 2021, with the Government's push on free schools to be factored in schools' estates.