The leader of an academy trust featured in a TV series highlighting school funding cuts has dismissed a minister’s claim it had “plenty of money” to fix its windows.

The six-part BBC2 series School, which centres on the Castle School Education Trust (CSET) in Gloucestershire, shows the effects of financial pressures on schools.

In the first episode, cameras filmed a science lab at the Castle School where pupils wear coats in winter because the trust did not enough money to fix broken windows.

In a House of Lords debate about school funding last week, schools minister Lord Agnew acknowledged CSET has “a number of challenges”.

But he added: “When I looked up the figures for the school condition allowance, this trust receives over £1 million from that a year.

“The school in question - I think it is called Marlwood [sic - it is Castle School] - is the biggest and, although we do not publish individual amounts per school, because the academy trust is free to use it as it sees fit, I can assure the House that there was plenty of money to deal with those windows.

“If it had a better call on its money than windows that increase heating costs, this is the sort of thing I get frustrated about. It is not all as one-sided as people think.”

Now William Roberts, chief executive of CSET, has told Tes that although it receives £1 million a year for its seven schools, it has a “backlog of what needs doing that runs to tens of millions of pounds”.

He said: “There is an issue with the windows not closing properly, but there is also an issue with the roof, and the floor, and the walls, and the heating, and basically everything about as it is a 50-year-old temporary building that is well beyond the end of its lifespan.”

Mr Roberts said CSET had a “bigger problem” than £1 million of capital funding could fix.

“Yes, of course, we could spend that money on replacing those windows,” he added. “But we would then not spend it on the things we have been spending it on this year, which is things like replacing a flat roof that leaks every time that it rains in a dining hall.

“We’ve spent it on replacing a boiler system that died completely over the winter and had to be completely replaced.

“We’ve used it at one of our primary schools where we have had to refurbish all of the communal areas and the staircase because they did not meet fire regulations.”

Mr Roberts added: “I think what Lord Agnew was saying in the House of Lords was ‘why can’t the trust manage to repair windows if they are getting £1 million a year’.

“Well, the reason is there’s a really big backlog and I would be really happy to share more information about that with him or with his officials.”