She obviously had not gone to school

I drove through McDonald's for breakfast this morning and the lady who took the order was perfectly understandable. Obviously she had not been to the Fast Food School for Mumbling, which I had thought was required for all workers at drive- through speakers. Fibber McGee explained the process once, in his case with regard to streetcar conductors. They start them off by putting a marble in their mouth, and if they can still be understood, then they add a marble, and so on until their speech become unintelligible. Then they graduate.