I had to write a review for Sean because he really is a top-notch TA.
Sean taught one of the three required discussion sections for the History of the World to 1450 course. I know what the term "discussion section" usually brings to mind: a small group of students, glancing at the clock every five minutes, each one thinking of that one golden piece of BS that they plan to say so that they will have spoken at least once that day. But not Sean's discussion section. Sean has an incredible knack for stimulating student discussion without making it feel forced. He is a genuinely nice guy who creates a comfortable environment for his students. Discussion flows so smoothly and so naturally that the hour-long section seems to pass in much less time. Discussion usually focused on the material covered that past week in lecture, and Sean would pay special attention to particularly confusing or complex topics. His clarification was an enormous help in understanding the otherwise overwhelming concepts of world history.
Outside of lecture, Sean was available nearly every hour of the day. He would typically respond to emails within several hours which was especially helpful when working on one of the two papers for this course.
On a final note, Sean connected to his students on a personal level. Before each discussion section started, he would ask everyone how they're doing and how their other classes are treating them. Sean's honest personality combined with his effective teaching style make him truly one of Columbia's best TAs.