"Contractors and materials should have been organised ready to arrive on site when schools finished in July, and subject to penalty clauses if they failed to complete by September."
There isn't enough capacity across the UK to get on site at this many schools simultaneously and no contractor would take on the work on those terms. Depending on where the RAAC is and how much of it there is it might not be possible to do everything that's needed in 6 weeks anyway, and you don't always know how long it's going to take until you've started.
I absolutely blame the government for not getting onto this sooner but let's not be unrealistic about the extent of what's needed to rectify this. What should have happened by now in/with the affected schools is a proper assessment of what if any decant is required and some sort of centralised effort to get portacabins lined up for the schools that need them.