New Plymouth Boys’ High School has a vertical house structure based around four well-known Old Boys. Each student in the school is allocated a House when they begin their education at the school.  Where there are brothers they are all placed in the same house. Day students are distributed alphabetically, based on their surname, into three Houses, Donnelly, Barak and Syme (A – H: Donnelly / I – P: Barak / Q – Z: Syme).  Students who reside in boarding are allocated, irrespective of their surname, to Hatherly House.

The House structure is based on vertical grouping with the 3 day-houses having 16 groups and the boarding house (Hatherly) having 8 groups. Each group has students from Year 9 through to Year 13 in it with a teacher in charge of each group. Each house has a teacher as Senior Housemaster and a Year 13 student as Head of House. Depending on where in the alphabet the student’s surname is depends on which house they are placed in.  For example a student whose surname begins with M would be in Barak house.  Each group has the first letter of their house (B, D or S) and a number eg. Barak 13 is called B13.