Former principal Joyce Beck addressed a crowd of at least 250 ex-pupils and staff members at an opening ceremony for the school's jubilee on Saturday.
She read a letter from one of the school's "most distinguished'' former pupils Carole McArthur, who now works at the University of Missouri as a teacher of immunology and was unable to attend.
The letter said not to give up on "lofty goals'', even if they seemed unlikely to come true, as belief and determination were key aspects to success.
"Over the years, as a result of a rich and diverse education which began in Kaitangata, I have been very fortunate to enjoy a fascinating life,'' the letter from Dr McArthur said. Former teacher Anne Davies (75) travelled from Abernyte in Scotland for the event.
She spent one year on an exchange in 1986 at the school.
About 30 teachers went on a similar exchange in New Zealand but Mrs Davies believed she was sent to the best school of the bunch.
She said the community at Kaitangata school treated her to a uniquely Kiwi experience.
Over its history, the school has boasted notable sports players, including Tony Brown and former international rugby referee Cliff McAuley, who spoke to the crowd about his memories of the school.
While Mr McAuley said he was not the "brightest tack'', he and other children from the school enjoyed playing games.
Mrs Beck said while it was clear school had changed in the past 150 years, education and helping young people were still core values of the school.
The two oldest surviving former pupils, Eric Bisset and Ann Walker, cut the commemorative cake together with the help of current youngest pupil Jamie Kennealy.
Festivities included photo opportunities, a performance by the school's kapa haka group, a cabaret on Saturday night and a church service yesterday.
