A picnic lunch and tours will be followed by drinks, dinner and dancing at BayPark ASB Arena Stadium Lounge.
On Sunday guests will be invited to mass at St Mary Immaculate Church.
Former principal of the school Sister Gabrielle O'Neill will be among the attendees.
She has maintained a close relationship with the school since her 12 years leading it from 1962 to 1974.
Sister Gabrielle said the school was originally fully staffed by nuns, with lay teachers arriving later.
She now lives with the other Sisters of St Joseph of Cluny next door to the school.
She was not the only one to have stayed close.
Mr Fullar said the school had six staff - five teachers and one teacher aide - who were once pupils. They were Bryan Crowe, Megan Akkerman and three sisters - Anna MacKinnon, Joanne Meehan and Nicola Meehan.