Although each college is composed of a full cross-section of students at Rice, they have over time developed their own traditions and "personalities". When students matriculate they are randomly assigned to one of the eleven colleges, although "legacy" exceptions are made for students whose siblings or parents have attended Rice. Students generally remain members of the college that they are assigned to for the duration of their undergraduate careers, even if they move off-campus at any point. Students are guaranteed on-campus housing for freshman year and two of the next three years; each college has its own system for determining allocation of the remaining spaces, collectively known as "Room Jacking". Students develop strong loyalties to their college and maintain friendly rivalry with other colleges, especially during events such as Beer Bike Race and O-Week. Colleges keep their rivalries alive by performing "jacks," or pranks, on each other, especially during O-Week and Willy Week. During Matriculation, Commencement, and other formal academic ceremonies, the colleges process in the order in which they were established.