I was in high school in tennessee in the late 1950's. In my opinion, high school math education was much better in those days than it is today say in Georgia, where I live now.
Although I did not learn calculus, I learned algebra and geometry well, as well as logic and set theory. Thus I had an excellent precalculus background to base my college study of calculus upon at Harvard.
Today, many high schools in Georgia do a poor job of teaching algebra and geometry, and although they present calculus to many students, those students do not seem to understand anything about any of these subjects when they reach college at UGA. Of course there is the danger that I am comparing my own preparation, as a merit scholar who went to Harvard, with that of an average student of today who goes to a state school. It is possible the average student in 1956 at my school was as weak as todays students are.
But my impression is that the quality of precalculus instruction in high school has declined in order to make time for a poor quality high school calculus course. Thus our students are even harder to teach in college than students were in the 1950's, because they must be taught things high school students used to know, before they can be retaught calculus properly.
College instruction has changed negatively as well, since it must be more remedial to make up for the decline in quality of high school education. Thus from my perspective as a teacher in a public state university, and a recent parent of high school students, math education appears now more sophisticated, but that is all flash and no substance, and the real education is worse than before.
At the end of the 1960's the SMSG program from NSF began an ambitious program of introducing better more substantial more modern materials into high school education, but this movement foundered totally because of poor or no training for teachers, and imitation "new math" textbooks that had no significant content. The actual SMSG texts from Yale were much better than the books then in use and many now in use but were not widely adopted.
The demise of teaching geometry from the original Euclid, which occurred in about 1910, is one of the most harmful events in US mathematical education. At least there were some similar books available in the 1950's. Currently, the geometry book of Harold Jacobs, which is good but not as good as Euclid, is as good as it gets in terms of high school books, and it is considered too hard to use by many systems.