The push towards open-plan rooms stems from research showing learning should be individualised, social and student-led - rather than a one-size-fits-all approach.
A white paper from CORE education said most schools were moving to the new teaching style: "However, the actual classrooms largely remain as they were originally designed, and still retain the suggestion of factory-style learning," the paper said.
Headmaster Tim O'Connor said because Grammar's teaching style was to teach content, rather than focussing on student-led learning, the 12-classroom block's layout fitted it better.
"Our teaching style is teacher-centered learning," headmaster Mr O'Connor said. "The key thing with the new classrooms are that they are wide not deep - so those in the back row are closer and it's all about the relationship between student and teacher."
It also allowed for students to move about the school more quickly, fitting with its demanding timetable of seven 40-minute periods per day.
Money for the building largely came from fundraising, with the Ministry of Education meeting one-third of the cost.
The Grammar way
•Teachers must wear professional dress - no short skirts for women, men must wear a tie.
•Classes are streamed according to academic ability.
•A relentless exam schedule - three times a year for juniors, four for seniors.
•Students do not usually bring electronic devices to class.