<p>Most if not all classes have TAs. What TAs do depends on the TA themselves and the class they’re TAing for. The professors teach the class, and the TAs handle the (usually) 1 hour discussion sections a week. Again, depending on the class and the TA’s attitude, they could give out HW answers, review materials, present materials in a different light than the professor, and some even have some nifty tricks for memorizing materials for the class like mnemonics. </p>
<p>For the clusters, I know some TAs for the IRD graded on actual quality of participation, while I heard a few just gave points for showing up. For the clusters, discussions are mandatory, and some TAs will allow students out early, while others will hold the students in until the very last second. They usually go over the reading for the week, and have some sort of open discussion about the lectures that went on. Some had some small projects and presentations that students had to do in discussion, and during the weeks before an essay is due, you spend most of the class time just peer reviewing each other’s drafts.</p>
<p>The main grade in the IRD class is based on essays, and so most people will go to a TAs office hours to have the TA revise their paper (since they are the graders afterall) to the point that the TA has run out of suggestions/criticisms.</p>