On September 22/23, we held the Australian Championships for RoboCup Junior. This year we saw over 140 teams and over 400 kids from all over Australia come to Canberra to show off their creations. I am constantly amazed at the ability of these students and what they are able to create. We make it a point to interview every team to make sure that the work is substantially their own (not some well meaning but overhelpful teacher or parent). I spoke to quite a few teams, who despite being in grade 10,11 or 12, knew more than I did after my first year of my Engineering Degree!
While not strictly a LEGO competition, given the ease with which LEGO can introduce students to robotics, we see a large percentage of competitors with NXT's (and even some RCX's!)
More info on RoboCup Junior Australia - www.robocupjunior.org.au