"Material and pervasive" it does not get much worse than that.
We are pleased the NAO has found no material inaccuracies in the financial statements of the department, the EFA and the 3,905 academy trusts included in this report. That might be because they stopped looking when they realised that the consolidation had been done so badly.
An adverse opinion isn't the same as saying 'we don't know (because of REASONS)'. It's saying 'I think not, thank you very much'.
The NAO didn't actually audit the 3,905 academy trusts either. So it would have been odd if they had found 'inaccuracies' (which isn't something they would report on anyway, true and fair != accurate (necessarily))