Only Nelson's Waimea College could manage to qualify alongside the group of Christchurch teams, losing to Shirley Boys' High in the third and fourth playoff.
The final two spots were taken out by Middleton Grange and Burnside High.
On the girls' side of the draw Christchurch Girls' came runners-up to Otago based St Hilda's Collegiate.
Following behind Christchurch Girls' High were fellow Christchurch teams Middleton Grange, Rangi Ruru and St Andrew's College.
Cashmere High School boys coach Ben Sheat said it wasn't a surprise that so many Canterbury sides were going to nationals.
"I really think that represents the strong local Thompson Trophy competition, which is making a lot more depth. "
Middleton Grange coach Tim Bennetts said:
"Christchurch teams benefit from the regular quality competition they receive in the weekly Thompson Trophy games, something other South Island organisations don't have."