Mr Jackson, who replaces retired rector Dr Paul Baker, was introduced by board of trustees chairman Bill Wright, and said he was "very, very honoured to be the 11th rector of WBHS".
"This is a very special day for me," he said.
He welcomed the new and returning pupils, described his position as one of the "great jobs" and vowed to be an accessible rector heavily involved in academic, cultural and sporting pursuits.
He implored the pupils to make the most of their opportunities, noting that Western culture was "user pays" and that education after high school could prove costly.
Pupils should set goals every day and treat each other, and faculty members, with respect, he said.
"The one type of person I despise is a bully. There is no tolerance [for bullying] here whatsoever."
The tone of his speech was the message of perseverance, with the words of Winston Churchill, who was asked what kept the allies fighting in World War 2 when "Hitler was at the door", acting as the central motif.
"Never give in, never, never, never, in nothing great and small, large or petty, never give in except to convictions of honour and good sense," he said.
That quality would be imbued in the school's pupils, and apparent in academics, cultural pursuits and on the sporting field, he said.
"I want [visiting schools] to know that they got a game; you might not win, but I want them to know they got a good game.
"I don't give in and neither will you. That's what a Waitakian is, someone who keeps going.
"Waitakians are a team, we support each other. Let's look forward to success together."
The assembly, attended by the board of trustees, staff, St Kevin's College principal Paul Olsen and Waitaki Mayor Alex Familton and wife Heather, began with the singing of the national anthem.
Deputy rector Tony van der Sluis led a moment of silence for former teacher Russell Drew, who died recently after three decades of service.
