It's stupid.
Many U.S. school teachers somewhat do the same. They don't want to name their child , for example, kevin, after knowing too many "bad" kevins. Basically, I think they do judge their names because they do associate names with their behavior. Which kids may just sense that type of judgement and act out. I mean, most have a issue with kids named Ethan (seriously) but I think they are the ones who brought on the cycle (every kids named ethan comes to school are greeted with low expectations from teachers)