Question one. How can we keep spending billions on school building while struggling with the biggest crisis in our public finances since the war? Not easy, is it? Even a grade A* economics student would struggle with this one.

Not many of us are putting our hands up and offering to pay more taxes, and anyone who suggests making a single nurse redundant needn’t bother standing at the next election. But as we publish our back to school issue this week, the conundrum facing politicians isn’t far from anyone’s mind: after all, the designing, costing and constructing of schools has become the bedrock of many firms’ order books.For those responsible for winning work, it has not yet turned into one of those recurring nightmares you get about sitting a big exam – projects are still reasonably plentiful, but as public borrowing reaches £175bn a year, even Gordon Brown is talking about tough decisions. And as Noble Francis points out, Alistair Darling has already said capital spending will be halved by 2014. All of which is ironic in so many ways.

For one thing, the building programme has just started behaving itself. After starting out as a slow learner, Building Schools for the Future is, as Tim Byles says, “firing on all cylinders”. True, there has been the problem of running a PFI programme with no private finance, and the college building programme (which PfS may take over) is better not mentioned, but Byles can rightly blow a few bars on his trumpet – 87 rebuilt schools are open, and 57 of them were finished in the past year. And to its credit, the government has come up with some joined-up thinking.

The academies, which had a lot of froth in their budgets, have been integrated with BSF, which should make for more efficient procurement, and Cabe has got some control over design, so the schools should be of a standard. But just when the problem child has pulled up its socks, we have the prospect of a wholesale change in the teaching staff. Nobody knows what the Tories are going to do with education spending, but before we go back to the underinvestment of the eighties, let’s hope they do a decent cost–benefit analysis.

It doesn’t help, of course, that we haven’t got the results of Labour’s big experiment – although it’s hard to read the story of the John Perryn school in Acton without concluding that the fabric of a school influences the performance of those who use it . Of course, there are many variables in a child’s development, but at least this is one that the government can control – and benefit from after pupils become taxpayers.

It seems that the Conservatives are minded to scrap or downsize PfS as they replace Labour’s target-led managerialism (aka paranoid control freakery) with “localism”. Chopping PfS might save money, but what about all the money that will be wasted by councils as they each try to reinvent the wheel? Then there are the economic and social benefits: the £6bn-a-year schools programme – unlike a South-eastern project like Crossrail – brings work across the country, and some of it will reach the smaller firms who need it most.

That’s not to say it wouldn’t be right to think about renewing schools by refurbishment, or even stretching the programme over a longer period. And although the PFI has been rather unfashionable of late, it’s still the best way for a fiscally challenged government to get work going. Nick Pollard, the chief executive of Bovis Lend Lease, says the industry could take on more risk if it would help, but that might be going a bit far (ask Jarvis how risky school work can be). Still, it shows there’s a will. So, reinventing PFI for a new generation of school building – now there’s an A level project for an eager 16 year old returning to school this week.