Mr O'Neill said their job was made easier because of the book The Heart of the Parapara and Field's Track by Ross Annabel and Marion Donald, who wrote about schools on State Highway 4.
Former pupils now living in Australia are interested in attending the centennial, which begins with registrations on March 30.
That afternoon, the celebrations will move to the YMCA Raukawa Adventure Centre, where a dinner and dance will be held that evening.
Accommodation is also available at the centre.
Former pupil Dr Paul Potaka, the principal at Nelson Central Intermediate, is master of ceremonies for the centennial.
Dr Potaka taught at Parihauhau School before he returned to teach at Kakatahi from 1975-78.
Dorothy MacLean was the first teacher appointed by the Education Department in March 1913 and the school opened in the Baddeleys' shearers quarters alongside the Whakawhiu Stream on April 7. Meanwhile, the actual school building had been approved and was built at the Rapiu Rd site, where it remained until 1926.
But all was not well and the department advised the settlers "that unless accommodation can be provided for the teacher, the school would be closed".
The roll numbers fluctuated between 18 and 24 until 1919, when the roll dropped to seven. By 1921, the roll was four. This year, the roll is once again at four.
An emergency meeting was called to try and boost the roll, but young families were not willing to live and work in the countryside.
Kakatahi is the only school on SH4 between Raetihi and Aberfeldy, near Whanganui. There is Ngamatea but it is on Field's Track, 45 minutes away.
For further information, go to the Kakatahi School Facebook page or contact Colleen O'Neill, 1134 Parapara Rd, RD3 Whanganui 4573, or email Robyn Mann: cowgirl@inspire.net.nz.