Vertical grouping in New Zealand secondary schools

Vertical grouping in secondary schools usually involves a 'house' system, where the school population is divided into roughly equal cross-sections, and within each house are an equal number of smaller class-sized groups also composed of vertical cross-sections. These groups, called 'house groups' or 'tutor groups' are an alternative to, and have many of the functions of, the traditional 'form' groups, which are (horizontally) composed of age-peers.