Kickin' It on Our Own - S2-E21
Corrected entry: When Ty takes over the Wasabi dojo, he punishes the current students by stripping them of their ranks and making them white belts again. He could not do that to the two black belts, Jack and Kim, because black belts are recognized by international organizations and a sensei cannot strip one of that rank without consent from said organization.
Correction: A black belt in Tae Kwon Do would not be recognized in a Kung Fu school; basically the Wasabi students are starting over in a new style, so Ty is well within his rights to make them white belts.