Collegium is the term used in the SCA for a set of classes on various Arts and Sciences topics. These tend to be run at major events such as Rowany Festival, but occasionally they are run on their own, for example Bunch of Classes. In some places, collegium events are called universities.
Grammatical difficulties with the word Collegium
Being a Latin word, the plural of Collegium is Collegia. As Collegium is already a word for something that there is more than one of most people get confused. Some people use the word Collegium to designate a single class and others will use the words Collegiums and Collegias. You could argue about it until you're blue in the face, but it's easier not to.