When I went to school, we did our math the same way our parents had done theirs.
The history books were not rewritten since the Depression (bad enough), so that was consistent.
There wasn't a new group of oppressed or perverted to learn about so we didn't offend them and gave them their "proper place" in history. There was consistency in our culture, warts and all.
Now there is a fluid course of genders and behaviours and racial divisions which must be accommodated to not exclude anyone nor give offense, and to smooth over entire horrors of History still being perpetrated so we don't offend those who have declared war, in one form or another against our country.
At least in WWII, in Korea and the Cold War, in Vietnam, we knew who the enemy was, and they have been increasingly teaching our children things that simply are not so..
True, but much of the dumbed down curriculum has been forced on schools by lib parents and so-called elite members of certain ethnicities.
But as you cited the math you were taught as the same as it was taught to your parents, there is basically only one good way to teach it.
By the fourth grade (or earlier), most people in academia know how students of particular ethnicities are performing differently from other students.
Whether it's taught the traditional way, like you and I were taught, or some other strange way, the students receiving the instruction learn by their own ways.
If all the students in a classroom that is experiencing diversity, all those students are receiving the same instruction from the teacher.
Some students process that info better than others
The only reason some people i.e. liberals are screaming and shouting about poor schools is because minorities (other than east Asians) tend to do much more poorly than whites. In other words, they're not processing the instruction they're receiving as well as white students.
I haven't been in a classroom for many, many decades, and the high school I went to was a parochial school.
But I would bet the way they teach math to grade school students 1-4 now is probably not much different than when I was in those grades sixty plus years ago.
Looking back, I've got a lot of criticisms of those schools I attended.
But the reason I wasn't a great student wasn't because of the faults of those schools.
Yours truly's predilection for playing sports and watching tv when I should have been studying played a far bigger role in my mediocre grades than what I was taught by my teachers and the school admin.