The n and b keys are right next to each other. I suppose that's a relatively easy error to make, especially if you use your right hand to hit the b key. Not the proper way to type, no, but I'm not exactly perfect in the proper way to type, either. I don't know if I've ever touched the right shift key of my computer ^_^
It does not seem like the teacher handled this very well, though. Like she doesn't get the gravity of the word.
Who's your favorite character from "Bend It Like Beckham"? And you can't say Beckham.