It's always about the money and the ideological enthusiasms of the teachers' unions and related groups. When I went to public schools there was no such thing as a teacher's aide, classes were anywhere from 26 to about 35, and the per pupil spending in inflation adjusted dollars was much lower than today. Given those "disadvantages" and others (e.g. the inflation adjusted income of middle income families then would qualify them "poor" today), children then got a far better education.
My school experience was the same as yours! I don't think I was ever in a class of less than 30 (one teacher who taught everything - music, art, phys ed.), nor was any building less than 100 years old! And yet -- surprise -- I got an excellent education! My current school district thinks every child should be attending classes in brand new, Taj Mahal buildings. You should see the schools they have built for millions when the old ones are still in good repair and could still be used. Ironically, the one building that they said could absolutely not be used for our students anymore was rented out to a neighboring school district when their new building was being built. Good enough for other children to use, but not for ours.