The usual manner in which a group photograph is taken is to blow a very large swath of light sufficient to illuminate the group. This is usually accomplished with something like a large umbrella flying over the head of the photographer, or to the side at say something less than a 45º angle. You want nice, pleasing, even light, with a nice chin shadow.
Somehow this didn’t seem appropriate for a group of dancers and their dramatic posing. Especially within the confines of a dance studio with some equally dramatic yet fairly grimy windows behind them. And a photographer working quickly with a smallish (for the group size) modifier already on his flash head.
So the solution, in this case, was to place said modifier at almost 90º to camera right, creating a split lighting situation. Instant drama. The light is not soft, yet not particularly hard either (witness the gradient on the shadow to the wall on the left). Add a wide angle lens (the utilitarian 24-70 racked all the way back to 24mm) – which exaggerates perspective for elements close to the camera – and you have a group portrait edgy enough for the talented CooperMorgan dance company.