I agree its not always "racism", but ultimately the main reason is still largely the same. They don't think their kids should mingle with the "others". Its the exact same logic of black school segregation during Jim Crow.

Sometimes for good reason. Observe what happened to people who tried to approach Sentinel island. That may seem extreme, but it's not my point. It's is that cultures are different and some are detrimental to the people of some other culture's wellbeing.