Georges River College Oatley Senior Campus is zoned for students from year 11 to 12 and covers the entire catchment area of junior campus of Georges River College. All three junior campus Georges River College Hurstville Boys, Peakhurst and Penshurst Girls Campus feed into the senior campus directly. It also accept significant amount of out of area students from what I read on their website. Following is a rough map of the catchment under my highlighted area.
As usual contact the school in question or Department of Education for the final confirmation and you can also access the full NSW and High School Catchment Map by following this link.