A system that was clear, simple and upon which employers and universities could rely to give them a good measure of a person's academic abilities, is now a shambles and doesn't give much away. Employers report having to send people with higher than average GCSE grades to remedial classes for Maths and English, and the universities are complaining that they can no longer trust A-levels and are re-introducing entrance exams (which is what in general A-levels were designed to replace!)
As has been said, the dumbing down started in 1988 for GCSEs and in 1990 for A-Levels, however it only really became significant after 1995.
It needs sorting out quickly.