"He was a bright boy, had a big future in front of him. He was extremely popular, larger than life and loved by both the students and staff, an infectious personality."
The school was told today at its assembly about what happened.
"[We said] that he'd been tragically killed last night and we'll do all that we we can to support his family and friends. We had a group of students today that have gathered to go and spend time together."
That included pupils from the city's girls college too.
"We've had a room that they can gather in today. We've provided food and drink and we've let them go off site to a close friend of Calum's. They are there now together, supporting each other."
Calum's friends have paid tribute to him on a Facebook page set up in his memory.
"Calum mate, you were taken way to (sic) quick man. There will never be someone like you to fill your spot again. You're one of a kind aye and that's what we will remember. Miss you like crazy man, love you," one message says.
"The boy who was admired for countless smiles, honoured for his caring personality, but most of all his big heart... Love you with all my heart," says another.
Next week the school's guidance team would be available if anyone needed help.
Meanwhile, Mr Mangan visited Calum's family and offered to help in any way he or the school could.
Pupils go on exam leave next week so it's unlikely a school memorial would be held.
Instead, Calum, who'd been at the school for five years, would be acknowledged at the leavers' dinner and tonight's sports awards.
Calum was a competitive swimmer and would spend a lot of time training in the school's weights rooms.
He's already got his NCEA level 3 and was part of the school's accelerated programme for bright pupils.
"Calum was involved in work experience and he was trialling for a builder's apprenticeship," Mr Mangan said.
Police said Calum was driving a Toyota that crossed the centre line and collided with an oncoming car on State Highway 29A.
Inquiries into the crash were continuing.
