It is hard not to be a bit dazzled by Building Schools for the Future.

After decades of under investment, the Government has pledged to rebuild or refurbish every secondary school in the country over the next 14 years.

Out will go drafty classrooms, leaky 1950s blocks and poorly-lit corridors where bullies can lurk.

In will come flexible learning spaces, curved glass walls, and environmentally-friendly buildings designed so they can be equipped with the latest computing technology.

Ministers have pledged vast sums of money for the project - more than pound;2 billion a year - and promised they will start on primary schools later.

Those who are still not impressed can visit the scheme’s website and marvel at the model designs for the scheme, drawn by some of Britain’s leading architects, and marvel at the stylishly-decorated social areas and “touchdown” zones for teachers designed to replace traditional staffrooms.

With all these wonderful developments, what could possibly be wrong?

For unions, the great concern is that roughly half of the work will be carried out through Private Finance Initiatives (PFIs). Private companies construct the buildings and are then paid annually to manage their cleaning, catering and other services, usually for a period of 25 years, after which they are returned to the local authority.

Representatives at the Trades Union Congress attacked the BSF scheme at their annual meeting in Brighton last month because of its reliance on PFI.

Kenneth Bell of Unison said: “This means cleaning, caretaking and catering are all at threatened with privatisation. Thousands of jobs are under threat from this - and councils are being forced down this road.”

Schools’ past experiences with PFI have been decidedly mixed with many reporting building delays and setbacks. Primary pupils in Richmond complained when they were left with ruined playgrounds and unfinished facilities after the contractor Jarvis suffered near-bankruptcy.

However, the six local authorities which will be the first to open BSF schools (Bristol, Bradford, Sheffield, Greenwich, Lewisham and Southwark) are optimistic they can learn from these mistakes.

Each hopes to rebuild at least one school by September 2007, with Sheffield aiming to finish its first by the end of this year. Not all secondaries in England can expect to get BSF-funded improvements, as the plan for Bristol illustrates.

It intends to refurbish only nine of its 17 schools through the scheme, starting with four next year and then a further five when the city gets money at a later date before 2020. The remaining schools are either already being refurbished through PFI, becoming academies, or are being rebuilt using council funds.

John Hiscox, a BSF project manager in Bristol, played down the threat to catering, cleaning and IT staff jobs saying contractors had to abide by employment transfer regulations and would often give their employees greater opportunities for promotion as they would be joining larger companies.

Mr Hiscox said an advantage of PFI was it placed greater pressure on the private companies involved to construct high-quality buildings.

“They are going to have to maintain the buildings for 25 years so it is not worth their while to come up a cheap quick-fix,” he said. “If they put windows in hard-to-reach places they are the ones who will have to find ways to clean them.”

He said that one potential problem was the “affordability gap” - the amount that councils pay to contractors above the amount they receive for the project for the Department for Education and Skills. He said the council was confident the future payments were realistic, but that many authorities would find them a strain on budgets as the number of their PFI projects increased.

Another risk with BSF is that building works will distract senior teachers from their jobs.

This would be particularly worrying for Bristol, which already languishes at the bottom of national league tables.

One of the first schools to be rebuilt will be Hartcliffe engineering college, which is situated in a crumbling 1959 building on an estate in the south of the city.

Malcolm Brown, head, believes the poor fabric of the building (“It doesn’t deserve the word design”) has been holding back his students, fewer than a quarter of whom gained at least five A* to C grades at GCSE last year. He said: “There are not enough doors in the right places so pupils are always having to use the fire exits and there is a loud noise as they crash open and shut.”

He is delighted that the school is to be rebuilt through BSF as part of a pound;35m campus which will also feature a primary school, pupil-referral unit and a FE college.

But he says the BSF process is highly time-consuming - taking up two to three days of his week - and sometimes frustrating, as he has had to re-explain the schools’ demands to different bidders.

Mr Brown does not regret his involvement though. “Part of my responsibility as a head is to plan the future of my school and I know that heads at schools in London which have left all this up to teams from their LEA are rueing that decision.”

www.bsf.gov.uk