All the time! We did small group work on Thursday and one of my students wanted to work with the para instead of me. He chose to keep his head down the whole period instead of working with me. My kids usually say thank you when we give them snacks. I would not bring anything in if they didn't/were rude about it and I would correct their behavior/take the treat away if it continues. I student teach in a low SES district. In some cases, I think kids are rude because they maybe don't know that they are coming off this way. I was at the board and a student used his hand to tell me to move over, I'm assuming he couldn't see. This came off as rude but I just said "Excuse me Ms..., I can't see, can you please move over?" The kid repeated it and it was fine.