Sister Greenlees said she needed help translating it because all the entries in that register and ones that followed for the next few years were in French.
This was because three of the four of the sisters who first started at the school were French, she said.
Sister Sarah came to the school herself in 1983 as a singing and music teacher before starting an accounting class.
In the 1990s she began working in the library, where she found a cupboard full of historical documents and photos relating to the school.
These had started to be compiled by her predecessors but was never finished so were put into the cupboard.
She took on the job of looking after the archives, requested a special room for them in the library rebuild about 20 years ago and has been maintaining it ever since.
"They are such treasures for the college ... I brought them out into the light."
She has now started digitising the records and is in the process of writing up information on each of the 5500 girls who have been through the school.
This will make it easier for families trying to find information on their ancestors, she said.
"One thing that amazes me is the foresight of the sisters to keep the registers and not throw them out.
"They are valuable because they not only record the history of the college, they are also part of the history of Maori education in New Zealand.
"We can boast of the first registered Maori nurse."
This information was found in a pile of letters between the Ministry of Education and the sisters in the early 1900s when the Napier Hospital Board created nursing scholarships for the students.
Sister Sarah said being able to show the archived material to past students, teachers and their families at the exhibition was incredibly rewarding.
"I'm very excited about it ... also seeing the girls who I used to teach. I think it's really worthwhile."
The Maori Catholic boarding school (formerly named the Providence) was one of the first schools established by the Sisters of Our Lady of the Missions in 1867.
Two sisters still live on school grounds to maintain the connection with the founding order.
The festivities will continue throughout the weekend with a book presentation by historian and author Malcolm Mulholland this morning, photos, a banquet dinner and other activities.