Look, there are racists around and I'm certainly not defending them. I speak here as a white person with Irish ancestry who has 2 black brothers, so we've come across our fair share of racism. What I am saying is that taking playground teasing and putting it into the category of racism is wrong.
Children have always picked up on differences. They'll turn your surname into a rude nickname, they'll notice any new haircut (my mother used to cut my hair, I was torn apart at school!), they'll tease you for having freckles, they'll tease you for wearing Tesco shoes. Yes the school should deal with it, but to make it racist means a whole load of paperwork for the school and the child's parents being informed.
Now my dd gets teased because of her Northern accent (we live down south). So in our case, I can only tell her to be proud and have a word with the teacher about teasing. But in the OP's case, that is racism is it? So two very similar cases of teasing are treated entirely differently and you think that's ok?
Children are not, by their nature, racists. They don't really have any concept of a racist. They just react to differences and unlike us adults they aren't discreet, they will talk about those differences and point them out. We should not stifle this because we, as a nation, are obsessed with racism.