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The competition involved stacking cups as fast as possible using three main routines known as the 3-3-3, the 3-6-3, and the cycle.
William who attends John McGlashan College, completed the 3-6-3 routine in 2.14sec and the cycle routine in 6.12sec, breaking the New Zealand record for both.
He was also placed second overall.
''Once you get fast it is hard to improve on your time,'' he said.
The participants were split into age groups then the top times from each group competed against each other and the overall fastest time was calculated by adding the times from all three rountines together.
William first saw the sport on YouTube over two years ago and is now part of the New Zealand Black Stacks team along with fellow pupil Ben Lovelock (17), who also competed in the competition.
Ben said he saw his cousins doing it about six years ago and decided to try it.
''It's such a simple concept but it's really good fun,'' he said.
Competitors had to use official mats and bottom-less cups which were provided by Speed Stacks from America.