This especially sucks for CS since a nontrivial portion of incoming CS students have programming experience but a large number have none. Using a 101 course as

This especially sucks for CS since a nontrivial portion of incoming CS students have programming experience but a large number have none. Using a 101 course as a weed out has the effect of stratifying these two groups. As one would expect, men are disproportionately likely to have prior programming experience so this process contributes to gender imbalances. CMU found that reorienting its curriculum to not place so much emphasis on prior programming experience in intro classes had a significant effect in reducing the number of women who tried CS and then left.