Good point.
I was in what amounts to an accelerated math program when I was in high school, and when we got to the calculus part I was lost, could not understand anything, and my grades quickly dropped to a D. I was 16 years old at the time.
Thirty something years later I'm back taking math classes at my local junior college. I only needed to get through college algebra for the program I was in, but was enjoying myself so much I took probability and statistics, and then signed up for calculus. I was 47 years old. I LOVED the calculus. It felt like a reward for all the algebra classes I'd taken. I comment on this to several of the math teachers at this school, and to a person they said, "Oh, Sheila. What most people don't understand is that math is developmental, and most 16 or 17 year olds are simply not ready for calculus, but they will be at 18 or 19."
I thought back on my experience and realized they were right. I also saw that exact same thing in my two very bright son. Couldn't do calculus at 16 or 17, but could a year or two later.
This is not to put down anyone here who did calculus at 14 and just loved it. You do understand you are NOT exactly like everyone else, don't you?
I'm certainly no expert in teaching math at the younger grades, but it's clear that some of this stuff is total crap.
Oh, and I'm old enough to remember before we had any special ed at all, back in the 1950's. The kinds of kids who later on would be in special ed were either allowed to flunk every other grade or so, or simply stopped going to school, if they were ever enrolled in the first place.
However, I'm going to defend showing your work in math class. It really is important. I wonder how a kid could make it through an entire school year and never get the message that the work had to be shown. Showing your work allows a kid who gets the wrong final answer, but who has thing right up to a point, to get partial credit. The teacher who marks the entire problem wrong when the student is correct up to a point is doing much more harm. More to the point, there should have been communication with the teacher about that issue. There's a reason for parent teacher conferences. The first report card with a D ought to have been a clue.