The festivities also included live music and food trucks.
School principal Anne Roughan said the event drew a large crowd of past pupils, families, staff and community members.
The celebrations of one of the oldest schools in the Waitaki district began on Friday afternoon with a welcome by Kakanui School pupils Hayden Carpenter, 12, and Aubree Johnstone, 11.
This was followed by a karakia, waiata, and guided tours of the school classrooms and grounds, while visitors also enjoyed afternoon tea in the marquee.
Ms Roughan said 155 years was a "huge milestone".
"We had a fantastic time. The good turnout reflected the deep sense of pride and community surrounding the school.
"Kakanui School has always been more than a place of learning," Ms Roughan said.
"It’s a place where friendships are made, where children grow in confidence and curiosity, and where a sense of belonging is nurtured."
One former pupil, Bill Walker, travelled from Canada to attend the festivities, Ms Roughan said.
The celebrations continued on Friday evening on the school grounds, with guests piped into the marquee by Rodney Elder.
A short welcome was followed by drinks and shared nibbles, while the rolling classroom displays and historic photos proved a major attraction.
A family fun day followed on Saturday, and the school grounds filled with food trucks, face painting, games, live music, and tours of the restored church next door, Ms Roughan said.
The official opening was held on Saturday morning, piped in by former pupil Janice Hayes.
Ms Roughan acknowledged the generations who had been part of the school since its founding in 1870.
A kowhai tree was planted, a plaque unveiled, and class photos taken. Those atttending then got to enjoy a slice of the anniversary cake made by Sonya Mathewson.
The celebrations concluded with an evening function, featuring a buffet meal and live music from local band Harbour Beat, and guests danced "late into the night".
The school was looking ahead to its next chapter while carrying forward the memories and connections celebrated over an unforgettable weekend, Ms Roughan said.
