I like how people poopooed the OP's concerns with "Don't be silly, why, at my child's school there are Polish kids etc..." Yeah, she said she's in a rural village with a class of 8 kids. Know the thing about rural villages? They're very, very, white-British. My family is lucky - our school is very multicultural. But when I was at high school, we literally had one black student. In the entire school. Because, rural village. And white posters insisting "Don't make problems where there aren't any."
Yes, all these ethnic folk, making a fuss. Can't see what their problem is, hey?
OK, so in reality? She might get some silly questions from the little kids, because chances are the other children may not have seen people of other nationalities around their village either, and hopefully if any of this escalates into mockery or bullying the school will deal with it well (and not just brush you off like above.) As they get older... honestly, yeah, it could be an issue. I guess it depends on the village, really. Whether it's the kind that all vote UKIP because of 'immigrants' even though they've never seen one. You'd only have to google for a Mumsnet thread about 'what racist comments have you received? to see how some people can be - albeit anywhere, it's true, but it's probably more likely in a place with no other ethnicities around.
YANBU OP. It's a valid concern.