As I've mentioned, I've seen it with certain specialized classes, such as Lindy aerials and Double Bug, as well as one ballroom instructor's workshop series (6 weeks each) for Viennese Waltz and Quickstep. In each of those cases, you had to have a partner just to get in; no signing up alone. Now, in the QS class, my partner came down with the flu partway through and was out for a few weeks, during which time I would learn and practice my part by myself, but then a foster couple would be assigned to me so that I could try it with a partner a few times. Oh, and one WCS teacher also required partners for one of her advanced classes. I would imagine that certain very advanced classes and classes for competition would also be likely be partner-required. Otherwise, "no partner required" does seem to be the norm, but then my view is biased by being involved with social dancers much more than with hard-core solid-metals (pun intended) ballies. @ Jenny: Performance classes! I completely forgot (or was trying to repress the memory)! In training for the performance we teamed up with a partner and stayed with that partner except for when the teacher or captain would order a specific rotation during a practice (eg, someone's partner wasn't there or the person is new and needs help learning the moves). Though again that is a special case, not a regular group class. The needs of the class dictate the presence and method of rotation. @DL: I also did a couple semesters of ballroom for PE (anything to get out of f***ing sports! -- back then (1969) PE was required every semester until you reached age 21, that requirement apparently intended to substitute for the prior requirement of two years ROTC for each male student; why else do you think that the ROTC armory was a favorite target of student protests?). I had already taken all the SCUBA classes they offered, to ballroom carried me through the rest of the way. In our case, the class rotated. But there wasn't any competition or performance training intended, only introduction to social dancing.