Civilisation then begins its downhill slide, and after another few hundred years, it slides into oblivion. If the teaching techniques and methods of assessing educational achievement remained constant and unchanged, this would be blatantly obvious. It would be demonstrated by a massive failure rate in examinations. This is why teaching techniques have been regularly changed, so that the techniques could be blamed for the inability to read, etc. Also, exams have changed.
Course work is more significant in assessment than it used to be.
Bad spelling is not penalised. Exams have been made easier. There are set quotas of passes which are awarded regardless of performance. The school league tables put pressure on schools to give the impression that they are doing well, with a high pass rate. However, no matter how these superficial factors cause a lowering of educational standards, we must recognise that the intelligence of the population can only decrease given the pressures of civilisation to increase the quantity of unintelligent children born in comparison to intelligent children.