The Wardens

Werewolf, Boto, Bear Walker, Loup-garou, Selkie, Ragshasa, Kanima, Skinwalker, Kitsune...
All are names of legendary creatures that shift from man to beast or beast to man, and they originate from ancient cultures all over the world. A common phenomena like this is shared despite the diversity and isolation of primitive societies because shapeshifters exist, and they coexisted with humans thousands of years ago. They come from their own world that is closely related to the human world and easily accessible through specific gateways located around Earth. But when the shapeshifters realized the human world had resources that made them superior, a faction of them became greedy and wanted it all for themselves. A civil war broke out among the shapeshifters between the dark group later dubbed the Skinwalkers by the Navajo and the shapeshifters who fought for the humans and peace. Good eventually won, but the humans had come to distrust all shapeshifters and forced them back to their own world. Eventually, history became legend and shapeshifters were washed away by fantasy.
Now, a school built over the only gate remaining educates young shapeshifters in the human world to one day become guardians of the gate and prevent Skinwalkers from trying to invade Earth again. But when some foolish boys accidentally provide an opening for the Skinwalkers, it's up to them and their new human friend to set things straight and save both worlds.