He said Otumoetai Intermediate School principal Henk Popping had taken him out for lunch and the college deputy principal, Bruce Farthing, had offered to switch roles for the day to pull off the surprise.
"But when this beautiful Mustang turned up, I thought there was something going on," Mr Randell said.
The retiring principal completed teacher training at the then College of Education in Auckland in 1970 before gaining his first teaching position at Rotorua Lakes High School, where he spent 17 years.
He held principal roles at Taihape College and Melville High School throughout the late 1980s and early 1990s before becoming principal at Otumoetai College in October 2000.
After nearly 18 years at the college, Mr Randell announced his retirement in April this year and was in tears as he said goodbye to his students and staff.
Mr Randell said it had been an "amazing time" as principal of the school and he pondered the word 'retirement'.
"It is a funny word and it hits you," he said. "I was driving to school this morning and as I came into the carpark I thought, 'Gee I only have to do this probably for another 30-odd days' and it is quite scary.
"You look back [at your career] and here I am 47 years later."
There was a big applause and an "awww" from the audience as Mr Randell choked back his appreciation for his wife and kissed her on the cheek.
"In life, you have got to have someone who looks after you and someone who supports you."
Tears continued as he thanked his staff and students for their support.
"This is all getting to me ... you have all been brilliant. Go for it you beauties."
His message to the students was to believe. "You never know what happens in this world. You have to believe in it and something will happen."
Mr Farthing said Mr Randell was a very personable man who was driven to achieve the very best for all those "in his charge".
"Family first, school second, has always been his [approach]when dealing with the staff and care and protection of young people has meant a determination never to exclude young people from education."
He thanked Mr Randell for his wisdom, energy and dedication and "invaluable input" to the college.
Head students, in farewell speeches at the assembly, said Mr Randell had shown his school to own both their success and mistakes.
"The Randell way has truly become the Otumoetai way."
Mr Randell received a standing ovation and three cheers as he was driven off in the white Mustang.
