In the first half, City dominated University with strong midfield play, which cut the University defence and kept goalkeeper Jareth Cocking busy.
James McKibbon got City on the board, sneaking the ball between Cocking and the post.
City held the lead for the rest of the half, but could not extend it after a barrage of missed opportunities.
The second half was almost the exact opposite of the first, with City completely falling apart and University running rampant.
Sandep Niah set up a Nick Saunders goal, before bagging one of his own a few minutes later.
Loose ball in front of goal cost City dearly, as Niah and Saunders tore the defence to pieces.
Matt Johl got two goals for University by pouncing on poor clearances, and James Kennedy also got in on the action.
Heath Dickson pulled one back for City on fulltime.
In the other games, Albany and Kings A drew 0-0 while the Tuataras were beaten 2-0 by University B.
In women's hockey, St Hilda's defended staunchly against top side University A but struggled to finish, with University claiming a 2-0 win.
It was a rapid-paced game from the start, with both teams looking athletic and displaying strong hits and traps.
The schoolgirls competed player for player in the midfield.
University tried to play its patterns but the St Hilda's defence was excellent.
When the students did eventually penetrate the circle they looked certain to score, but St Hilda's goalkeeper Ginny Wilson made a dramatic save.
St Hilda's then won a penalty corner but it was poorly taken.
It looked as if the game could go scoreless until the University forwards put three fine passes together, drawing the 'keeper out for Jamie Wiles to pop the ball into the goal.
After halftime, University started to dominate possession.
Led by Lydia Cooke, the students began to stretch out their game, passing well up the left.
Speedy Anna McConachy put a cross in from the right post and Kirsty Sclater scored a goal similar to University's first.
St Hilda's then fought back, with Kate Kernaghan working hard.
But with individuals trying to do too much, the school team tended to hold the ball a fraction too long.
Kristin Tizard had an outstanding game at left half.
In other games, Momona and Taieri drew 2-2 and Momona B upset City Highlanders 2-1.
