I think snooty is a bit old-fashioned- stuck-up is more common I think nowadays (in BrE). The noun toff for someone upper-class has made a bit of a comeback- there was a documentary about the current prime minister a few years ago called Toff at the top, and I have heard it used a bit since. Upper crust is another way of saying upper class. I am not sure what you mean by changing to it, but people may use it to sound less elitist or divisive.
Student or Learner