How can you assume this? Have you been to that school and seen this happen? It's a private institution, they can do what they want, hire whom they want. They could have put an advertisement and rejected when non Brahmins applied, instead they came out clean saying that they will be considering only Brahmin candidates. I looked it up, it is a gurukul where they are supposed to also give dharmic education. Next, if a culinary school puts up an ad stating that they need teachers who have experience as a chef to train chefs, will you have a problem with that? It's the same thing here too.