Generally, children not picked on based on race. But kids still prefer to mix with those they are famiiar with, is it the same with adults?
My son is in a school with 99 % white. He has no issue making friends, though it was abit tough in the begining. Have to be thick skin, and try to make friends. If you are shrinking violet, it may be more difficult to make friends in schools that are predominant white. Sometimes, kids do say insensitive things. But usually being insensitive, not done purposely.
In most primary schools, there is at least teacher on school yard duty. If you have concern about your kid fitting in as a miniority, there are schools around that 80 % of the school are asians. But for me, I will not put the kid in the school, becos it is an unrealistic demographics. He has learnt some point in time, that he needs to adapt and know how to integrate into real world. He is different from his school mates, and he has to deal with it. And sometimes our values are different.
Usually catholic schools and private schools have less instances of bullying and better discipline.