You might want to look at Koonung Secondary college which is rapidly improving and offers excellent facilities for sports, arts as well as academic results. As a past parent I can happily say that Iw as very impressed with the school and how it is run.
For public high schools, and provided you live within the school zone, Camberwell High School has a fantastic reputation; so much that it has a waiting list for people outside the zone who want to enrol their kids. If you have girls, Canterbury Girls Secondary is also a great option. Both are academically excellent. Both of my kids went to Camberwell High and loved it.