each successive generation has been rather dumbed down compared to their predecessive generations for quite a while already.
I guess it depends in what field you are talking about. If you look at the British education system, for example, then yes, I’d say that successive generations have dumbed down significantly in the field of classical scholarship. I’ve heard it said, probably not without justification, than a schoolboy leaving an English public school in the latter half of the 19th century probably knew as much Greek and Latin as a student leaving a British university with a degree in classics does today. Public schoolboys used to be given assignments like, ‘Translate “The Charge of the Light Brigade” into Latin in the style of Virgil’, or, ‘Write an account of the Battle of Waterloo in Greek in the style of Thucydides’. The best public schools also taught Hebrew and even Arabic.
The teaching of science, on the other hand, is in fact much stronger now than it would have been even half a century ago. Admittedly, people will argue, for example, that the standard of A-level physics today is poorer than the standard of A-level physics 30 or 40 years ago. This, however, focuses narrowly on the level of attainment among the very best students. I would wager that probably more young people know more about physics today than they did 30 or 40 years ago or certainly 50 or 60 years ago when many students would simply not have studied physics at all.
One could also look at subjects such as history and English literature. Some people will argue that standards have dumbed down because students today are required to memorise fewer facts and fewer texts. I would argue that standards have in fact risen because students are instead expected to learn skills and to develop independent and original ideas. When I talk to people aged around 70 and above most of what they remember from history and English literature at school was being made to memorise things.
I can’t speak for all parts of the world, but in the UK the school leaving age has steadily risen from the late 19th century down to the early 21st century. Adult literacy rates have risen steadily throughout the developed world. I can’t speak for countries other than the UK, but until well into the second half of the 20th century it was quite normal for non-graduates, and even people with no qualifications at all, to become teachers. Now virtually every teacher in the UK has both a degree and a teaching qualification.
As I say, people can easily point to areas in which standards today appear to be poorer than standards two or three generations ago, but I think that this is often a selective sampling of the evidence. I would say that standards have in fact risen overall.