It is simple: "Will you maintain real terms per pupil funding for schools over the next Parliament?"
At the leaders debate, Theresa May couldn't answer. Her response: "Nobody can guarantee the real terms per pupil funding increase.".
Which is odd, as Labour is promising exactly that. We know the increse in pupil nunbers expected over the next five years and we know that simply increasing funding in line with inflation means a reduction in the funding per pupil.
The Conservative manifesto claims that funding will be increased in real terms, but makes no mention of being maintained in line wtih pupil numbers. There is no doubt what this means. Last December the National Audit Office estimated a £3 billion shortfall. After the extra that Theresa May has promised, this still leaves a shortfall of £2.2 billion per year. (Detail here)
The Institute of Fiscal Studies found that, even after the £4 billion extra, Conservative plans meant a reduction of 6.9% in school funding by 2022. (More here)
The picture is clear. A Conservative government would mean five years of cuts for schools, five years of teacher job losses.
As one young person said on Newsnight last night, "austerity is an ideological choice". We can choose to reduce school funding or we can choose to increase it.
In this election there are knowns and unknowns. We do not really know how Brexit will turn out or who will be the best negotiator. But we do know what will happen to schools. If you know any parent, teacher or other school employee who is thinking of voting Conservative, get them to check the excellent School Cuts web site to find out what their school will lose.
Make sure anybody thinking of voting Tory knows what this will mean for their schoola nd their community.
And any chance you get, ask Conservative politicians "can you guarantee real terms per pupil funding?". Because they won't.
I checked my local secondary, where my three children went to school. The projection is shocking: