No one is born racist, parents and peers make people that way, and it would seem the school is largely responsible in this case. If you are going to take such a large influx of immigrant children into your school you should be doing a lot more to make the children mix and see their similarities rather than allowing them so fester on differences. As for the parents splitting the school yard in two come hometime, makes you wonder who the kids really are.
However, it doesn't matter what the circumstances are or what country you come from, in this country you never harm a child, not yours nor anyone elses, regardless of what the little $hits have done to provoke you. All that is doing is teaching these kids that violence is acceptable, then they grow to teenagers and we all start panicking about their aggressive behaviour, wondering where it came from.
This woman should, not could, be charged, and the boy should be made to apologise infront of the whole school for his behaviour. It would appear that perspective has been lost if the childs actions warrant the same attention as the womans.