I've noticed that primary school children make similar comments in the presence of my twin grandsons, who are in reception class. It happens during playtime and after-school play, when the dinner-time assistants are supervising the children. They repeat what has been said, not understanding that it's an insult. My daughter and I have been picking this issue up since they started school in September. My daughter and other mums have spoken to the reception class teacher and the head, who are addressing it with the children. My grandsons don't really get why we are concerned, as they are only 4, but it will sink in eventually.
The other day, one of them yelled 'watch, nana' and started dancing like the 'Gangnam Style' video, which is fun, but quite disconcerting to see a 4 year-old parroting 'Hey, sexy ladeee...ooh, ah ah ah!' My daughter substitutes other words for him to sing, and we know the fad will pass. It's such a challenge to balance the benefits of mixing with children of all ages, with the influences that we don't want them to be exposed to,