The Scottish Executive's £2bn school building programme has been marred by poor planning and shoddy workmanship, according to a survey of teachers.
Hundreds of schools are being built or refurbished
The EIS union's study heard complaints of narrow corridors and leaking roofs.
General secretary Ronnie Smith said some of the work carried out to date represented a missed opportunity.
But the executive said the study was already out of date as education authorities had learned from problems with the first round of buildings.
The executive is planning the country's largest ever school construction programme, with 300 being built or refurbished by 2009.
The work is mainly being carried out under private finance schemes.
The overhaul has been welcomed by the EIS, Scotland's largest teaching union.
However, Mr Smith claimed that designers had ultimately failed to listen to the staff who will work in the buildings every day.
He told BBC Radio's Good Morning Scotland programme: "The condition of much of Scotland's school estate is so appalling that any improvement and modernisation is greatly welcome and we do welcome the investment that is being made.
"But we think an opportunity is being missed - a real once in a lifetime opportunity - to produce real, high quality, fit for purpose buildings."
Among the flaws identified in the survey were poor soundproofing and discipline problems caused by small playgrounds outside, cramped conditions inside, inadequate insulation and poor water supplies.