Since 2010 and the introduction of austerity, government departments have faced some of the biggest cut to budgets in decades. Spending reviews, efficiency savings and a tight fisted Treasury have seen, for example, DCLG, DfT and DEFRA face cuts of up to 30%.

However, one policy area that has escaped reasonably unscathed has been the school budget. In fact, school spending increased between 2011 and 2015, by 3%, or 0.6% when increased pupil numbers is taken into account.

At the 2015 General Election, the Conservatives pledged in their manifesto to protect day to day education spending in cash terms. Note – cash terms.

This is proving a crucial distinction. Increased pupil numbers, inflation and changes to the way schools pay National Insurance have meant that the overheads faced by schools have increased, and will continue to grow, dramatically. Budgets, even without direct central cuts, are growing tighter. So tight in fact that some schools in Surrey have claimed that they may be forced to operate four day weeks.

The Institute of Fiscal Studies and National Audit Office have pinned exact figures to this. By 2020 schools will be expected to work with 8% less than they have currently. £3.2 billion of annual funding cuts will need to be found. 60% of secondary schools are already operating a deficit, with the average being £326,000.

So when Justine Greening stood up in the Commons this week to deliver a statement on the next stage of the Government’s introduction of a fairer funding formula for schools, one could be forgiven for wondering if it even really mattered.

But clearly it does.

Yes, the pot is getting smaller. But that doesn’t mean it shouldn’t be shared out as fairly as possible and, quite clearly, the current system is not fair.

Money is currently allocated to local authorities, and therefore schools, on the basis of archaic and in some cases irrelevant criteria that take no notice of disadvantage or other factors that may recommend greater investment. To take just one example offered during responses to Greening’s statement, schools in Solihull receive £1300 per pupil per year less than those in nearby Birmingham for no discernible reason.

The new formula should tackle this kind of discrepancy. But, with a limited pot, if some schools are going to receive more in the future, by necessity, some will receive less. And that’s where the major problem lies. While the Government will limit any reduction to a school’s budget to 3% per pupil, and no more than 1.5% per pupil per year, some schools already faced with 8% cuts are simply going to have to cut back further.

The political problem for the Government is that there’s only one obvious place to slash. Class sizes.

By simple maths, if you have more children in a class, you need fewer teachers overall and can save money on salaries. You could even pay the remaining teachers a better salary.

But with bigger classes come heavier workloads and, as we know, teacher workload is demoralising the profession. Schools are finding it harder to fill vacancies and losing valuable experience that will be vital if the pupil to teacher ratio is to increase.

And that’s before you even start to think about the political intricacies of telling parents that their kids’ classrooms are going to become even more packed. It will be a brave politician who risks the wrath of the electorate with that policy.

We’ve spent years debating the crisis of NHS funding. The crisis facing our education system is only just looming on the horizon. It’s time for politicians to learn the lessons of health funding and act decisively now before it’s too late.