P.S. 9: 3 schools within a school?

I'm starting this thread to ask for opinions from people familiar with P.S. 9. I have read that PS 9 houses 3 different programs in its site: A G&T program for kids from all over district 3, but mostly within the zoned area, who score above 90%; a program called Anderson which is described as "Highly selective"; and a program called Renaissance, which is mostly for the minority kids who didn't get into the other 2. So, my question, if anybody knows, is: how does the "selective Anderson program" selects? is it within zone, district? is by test scores? does it overlap with the G&T? what is its purpose? etc.