Running undergraduate tutorials and labs is a component of graduate students' training at most departments in North American universities. The experience is meant to prepare graduate students for the transition into academia, if they wish (and are fortunate enough to land a position), and to help departments manage teaching loads. TAs typically deliver material provided by the course instructor, help students better understand course concepts, invigilate quizzes and exams, and grade exams and homework assignments. How big is the change when a TA transitions from providing support to teaching the course? Earlier this year, I found out firsthand.