My girls go to gymrep in Quebec every year. Oldest has been for four years, it was the first year for little Bog last years, they would live there for the whole summer if I would let them. They are always challenged, the groups are loosely based on levels, but within each group girls work on skills that they are able to.
www.gymrep.com check it out, it's very cool and we love the outdoor aspect of the programme, also great French immersion. There were girls from the US, Mexico and France there last year. Coaches come from all over Canada and France. Activity supervisors come from Canada, UK and even Australia.
Also it is a great deal pricewise.