I hope people don't believe that there was ever a real teacher making that speech. It have as many versions as the Bible. BRUHAHAHAHAHAHAHAHAHAH! It's a hate speech anyway to say that only one race is welcomed especially in a public school. They named the different races in one version.
See here http://www.snopes.com/politics/soapbox/principal.asp to see what Snopes says about it's origin, read the different versions and how it is connected to radio white supremacy hate.