Project Runway went back to high school this week as the designers helped their student models get ready for prom -- one of the most important nights in a girl's life, as Heidi says. All of the designers had to work with their teen clients -- and clients' mothers -- on their concepts, and while most didn't have a problem, Christian found his client to be rather difficult, and let the judges know.   Other designers, like Rami and Ricki, may have been confident in their designs, but the judges weren't too keen on them. In the end, Christian's inability to take charge put him in the bottom two, but the judges found that Kevin's too-mature red dress should send him home instead.   The judges, including guest judge Gilles Mendel, found Victorya's short blue sheath and Sweet P's long champagne ensemble the most appropriate, and the win went to Victorya.