<p>Well I think the first replier was wrong about first year, all of those drops are due to more general courses: intro calc, intro physics, intro chem, etc. And yes, they account for probably most STEM drops.</p>
<p>But every STEM major has a second-year sequence that is the first “majors only” class where things get significantly harder than the first year.</p>
<p>Being an engineering physics major (so I’m studying physics and CS) I got the joy of going through two at the same time: the year-long classical mechanics/mathematical methods class (not the calc-based physics sequence that everybody takes) and the year-long component-based software design sequence, that was taught in my school’s proprietary language…that had limited support for the assignment operator. Both of these classes were at least one order of magnitude more difficult than first-year STEM weeders because it was the real deal. I’m sure every STEM major has a lot of second-year drops because of these types of sequences.</p>
<p>For the physics sequence, angular momentum in three dimensions was easily the most difficult part of the class and I’d wager anybody who switched out of physics did so because of it (or just poor math preparation).</p>
<p>For the CS sequence, I’d say searching/sorting with trees, using pointers, using recursion, and using first-order logic to describe algorithms weeded out lots of people.</p>