If you go to selective schools, no matter what you think, you're probably going to have to be very accepting of other cultures. If you're xenophobic you're going to have problems in a selective school. I myself am caucasian (eastern european), and there is only one other person from the same region in my whole grade. Personally I have no problem with this, although sometimes it is quite odd being white and part of the minority. But I will say, asians are unfairly stereotyped, hahahaha.
Otherwise, I think selective schools are more for those who are driven. In selective schools, I think your internal assessments are quite crucial if you aim to do well - since you're competing at such a high level, your standard level won't cut it if you want to get good marks. Of course, there isn't no such thing as unhealthy competition - not naming names, but there are a few people at our school who might... um... be a bit OVERcompetitive. Our grade in particular compared to others at our school is strongly competitive, so much so that people will refuse to share any sort of materials with you until after trials. So, it's much more necessary to have the drive to be able to learn by yourself, and have a greater understanding of what you're learning.
And yes, they are government schools. I still think it's a bit unfair that in our school, the girls get two toilets with perfect mirrors, as opposed to the guys getting one huge dirty smelly one with a piece of rusty metal for a mirror. hahahaha.