To accommodate the new vertical tutor groups, a House system was devised, comprising six houses, one of which every student is a member. Most of the staff are also assigned to a house. Each house contains fourteen tutor groups and is led by a "Head of House" and an "Assistant Head of House", titles which are sometimes abbreviated to HOH and AHOH, respectively. Traditional "Heads of Year" still exist, although their role has greatly diminished with the arrival of "Heads of House".