Performance being bimodal doesn’t mean that aptitude is bimodal, though. Different teaching styles may have different transfer functions, as it were.
Trivially, consider a teacher who only teaches at the level of the highest-aptitude students and allows no remedial or catch-up work for the lower-level ones, versus a teacher who only teaches at the level of the lowest-aptitude students and allows no enrichment for the gifted ones. We’d expect the former to produce bimodal levels of student performance given normally-distributed aptitudes (because almost everyone is left behind and performs very poorly, while the top students excel), while the latter would tend to produce performance distributions that were flatter than the aptitude distribution (because nobody is really allowed to excel).
I think they claimed that bimodal performance was typical for CS, which if true* would require CS teaching to be systematically biased in a way that doesn’t happen in other subjects in order to produce the effect, which strikes me as possible but unlikely.
* I wish they had given more statistics on this, IIRC it was a bit anecdotal.
Performance being bimodal doesn’t mean that aptitude is bimodal, though. Different teaching styles may have different transfer functions, as it were.
Trivially, consider a teacher who only teaches at the level of the highest-aptitude students and allows no remedial or catch-up work for the lower-level ones, versus a teacher who only teaches at the level of the lowest-aptitude students and allows no enrichment for the gifted ones. We’d expect the former to produce bimodal levels of student performance given normally-distributed aptitudes (because almost everyone is left behind and performs very poorly, while the top students excel), while the latter would tend to produce performance distributions that were flatter than the aptitude distribution (because nobody is really allowed to excel).
I think they claimed that bimodal performance was typical for CS, which if true* would require CS teaching to be systematically biased in a way that doesn’t happen in other subjects in order to produce the effect, which strikes me as possible but unlikely.
* I wish they had given more statistics on this, IIRC it was a bit anecdotal.