I actually have direct experience getting a (I would guess) 95 IQ student to understand precalculus, tutoring for a few months back when I was a high school stu

I actually have direct experience getting a (I would guess) 95 IQ student to understand precalculus, tutoring for a few months back when I was a high school student ~15 years ago. She got an A, after having had a string of Cs in every prior high school math course, and not being properly fluent with 9th grade algebra at the beginning of the year. [I don’t say this to brag; I expect any competent tutor can achieve the same thing with a typical below-average student if the student is motivated and they get lots of 1-on-1 time.] However, I can well believe that a 95 IQ student who was dramatically unprepared at the beginning of the year and believes himself to be an irredeemable failure will have a lot of trouble in a standard lecture + homework drills format high school precalculus course taught by a teacher with no time to help him catch up on remedial material at his current level of understanding, give him any special attention, or make the class material engaging enough to give him reason to care. In that context, failure (or scraping by with an undeserved C) is the obvious outcome, but can’t fairly be blamed on the student’s effort during that year or some kind of mental deficiency. (Personally, I skipped half of precalculus and somewhat wish I had skipped the other half; I found it to be an uninspired grab-bag of disconnected topics, with much too rote a focus.)