best school for year 7 and year8??

hi,
I am a permanent resident of Australia and would be moving to Sydney in nov 2011. my kids will be going to year 7 (boy) and year 8(girl). I want to enroll them into a selective school but i guess they have missed the normal procedure of selective school entrance test.
Can someone guide me how to get admission for them , which school would be good for them and in which suburb.....i am very confused about the choice of suburb and school ....
Please guide......
Ruchi