Under-pressure Education Secretary Gillian Keegan is visiting a school affected by the crumbling concrete crisis as thousands of pupils have been told to stay at home.

The Cabinet minister will be meeting school leaders and MPs in Essex, one of the areas worst hit by reinforced autoclaved aerated concrete (Raac), on Thursday.

She will be visiting a school with mitigations in place, rather than one of those forced to close completely just as students prepared to return for the new school year.

Ms Keegan ordered more than 100 schools and colleges to make either full or partial closures last week after she received new evidence over the concrete’s collapse risk.

She has provoked anger after she was caught on camera asking why no-one says “you’ve done a f****** good job” while “everyone else has sat on their arse and done nothing”.

The Education Secretary is not expected to do any media at the school visit.

A list published by the Department for Education (DfE) shows 147 schools have been affected so far by Raac, with 19 forced to delay the start of term.

Four have had to switch to remote learning for all students, and an additional 20 have had to offer some remote learning.

Six major unions representing school staff have written to Ms Keegan demanding she sets out how many schools suspect having Raac but are yet to have been investigated or surveyed.

We have taken a proactive and cautious response. But I think we should do that. We're talking about children and children's safety going to schools

With the National Education Union, Unison and the National Association of Head Teachers among the signatories, they have also demanded to know the deadline for clearing all schools of the dangerous concrete.

They fear the level of information from the DfE so far may not “reflect the full extent of the problem”.

Ministers have sought to level some blame for a delay in getting the full information together on school leaders.

Ms Keegan told school chiefs on Tuesday yet to respond to a survey on the possible presence of Raac to “get off their backsides” and respond.

Science Secretary Michelle Donelan defended her Cabinet colleague on Thursday, rejecting any suggestion an overly cautious approach had opened a “Pandora’s box” for other departments with Raac-affected buildings.

“No, absolutely not. We have taken a proactive and cautious response. But I think we should do that. We’re talking about children and children’s safety going to schools. It would be wrong if we did anything but,” she told LBC.