The sport is called
Mage Tower
There is an intense rivalry between the Colleges and they battle that out in magical duels. It is part of Strixhaven's special sport called Mage Tower. The rules are simple: two opposing teams meet in the school's large stadion alongside their mascots. There are three phases of play. Each mascot sits on a tower and the goal is to steal the opposing team's mascot and transport it over to their own side. The use of all magic is legal, except that which would physically harm opponents, mascots or somebody in the stands, or damage the stadium. Each phase lasts twenty minutes, and then a winner is declared.
Here is the video with the info
I will obviously include it in the lore thread you can find under Magic Forum -> General Discussions as soon as we actually have an article from Wizards on the matter.