Having tutored at a Post-graduate only college with world wide intake my observations are:
Between 1990 and 1997 the standards of, both general and specialist, education achieved by UK students deteriorated significantly, that of foreign students did not or in the case of some countries improved.
I always felt somewhat ashamed when it became apparent that a German student's standard of English was better than that of an English one.
My ex wife taught at one of the top specialist feeder colleges for the above, she resigned because she was not allowed to correct the students work either specialist or general, and felt that in reality this diktat meant that they would not be able to learn properly.
Another ex who had 3 teenagers (early 2000's) had a 15 year old boy who had been convinced by his school that he would pass, I think it was 8, all his gcse's, he applied to the local Uni and was given a provisional place, he failed all of them and ended up sorting the dirty linen for the laundry at a local hotel.
In the early 1980's I applied to take an evening course in Vehicle chassis design at Bolton tech, it was run in conjunction with Leyland Truck division for their trainee engineers (I was doing it just out of interest). The course was cancelled because no one from Leyland enrolled.
I work with a mother of 2 girls, one 34 and the other 14, asked if she notices a difference in educational standards she gazes skyward and sighs before saying yes massive (and not in the right direction).
I could go on and on but there's no point, successive governments have allowed or promoted the destruction of the UK educational system, aided and abetted by civil servants and a group of teaching unions that regard "teaching" as a fundamental breach of the children's human rights.
If the Ipod factory was staffed by workers who had a QC failure rate as high as our schools have then they would sack the lot and re-staff the factory, there's no way that can be done to the teachers as it is often their basic training that's the (politicised) problem.