Taieri College accounts manager and reunion committee member Sue Brinsdon, said preparations for the anniversary were well under way.
A reunion was scheduled last year, but had to be postponed because of Covid-19.
Ms Brinsdon said another committee member, Kristy Compton, had the idea for the pupils to form the 150 as a lead-in to the main celebrations at Labour Weekend.
The celebrations would start with a high tea and a decade of photos at the college.
A gala dinner and dance would be held later on the Saturday at the Taieri Rugby Football Club.
The celebrations would wrap up with a "Sunday Funday" where family and friends are welcome.
Taieri College was formerly called The Taieri High School and, before 1956, the Mosgiel District High School.
