Yes to ZS's post. Also-- getting MY first C from one of them in Algebra I as a seventh grader is what made me so utterly sure that I was a "bad" student-- I just didn't know it...

and that I was (evidently) particularly bad at mathematics. This impression was fully reinforced by encounters with two MORE math teachers like this during my high school years-- one of them fully competent (well, apparently-- he taught calculus, anyway) but mustering such an intense personal dislike of me that he actually TOLD my mother during a conference-- even knowing that she was a teacher herself, and in front of me, no less-- that the reason I wasn't doing better in his class was that he "just didn't like me very much." The other one was so appallingly incompetent that I am astonished that she continued to be employed by the district. No-- I'm very much afraid that once one ventures above elementary grades, mathematics instruction in public schools is VERY hit-or-miss.

And yes-- it matters. It particularly matters to girls, who are more likely to take a fixed mindset with aptitude in STEM, and far more likely to be teacher-pleasers who internalize apparent failure.

I didn't recover fully until differential equations, taken under duress during my senior year of college. Man, I felt like Cinderella had finally gotten to go to the ball. But I have never really gotten over it. I assume that pretty much every one of my peers (meaning those with similar intellect and education) is better at math than I am. This is clearly not the case. But the alternative explanation-- that I had not one, not two, but THREE capricious and hostile teachers who made it their mission to suck the joy and animus from math students-- seems less plausible than the alternative presented by imposter syndrome.

So no-- this kind of messaging to students at this particular developmental juncture is incredibly damaging. My lack of confidence with mathematics really held me back in an area of strength and passion.

Schrödinger's cat walks into a bar. And doesn't.