<p>In lecture classes, TAs do the grading, though there is some effort by professors to ensure consistency of standards (and some professors will choose to do some of the grading). In seminar classes, professors do all the grading. </p>
<p>But remember that TAs at Yale are all graduate students (and almost exclusively PhD students, though also the occasional law school student) - and in most cases they are at one of the very top departments in their field - they’re plenty capable of grading undergrad essays and giving good feedback. Obviously some don’t give useful feedback, but the same is true of some professors. It’s a different situation from Williams, which has no grad students, meaning that there is no alternative to having professors do the grading other than to use undergrads as graders. Williams (I believe) does not do that, but a rather large number of universities (including some very good ones) use undergrad TAs, and even have those TAs grading. This is worth keeping in mind - TAs are not the same at every university that uses them, and I’m far happier having grad students at a top grad program leading my sections and grading my work than to have a fellow undergrad doing the same.</p>