From a personal point of view, I wouldn't touch Sheldon. They are way too strict and I know some really good kids who are being told off for having the wrong coat, being sent home for not having one of the correct haircuts (local hairdressers are aware what is required if a kid is at Sheldon). I find it very sterile and lacking warmth. I know a few people with kids there and it works for them. I also know a number of people whose kids have hated it - it takes conformity to a whole new level.
I have heard very good things about Ormiston for the Juniors. Still fairly strict but more about the individual, rather than the image it needs to portray. They do put the pressure on when they get to Senior though, which is what put us off sending our son there (he would've been in the top years).
There are many great state and religious schools (Lutheran, Catholic) in the area too. If you have a kid that is going to work hard, dome of these really look at the whole person, not just grades. Ormiston State is great, along with Bayview. Kimberley College has a more holistic approach too.
JPC is also a good school, but is a fair way from the other two, which are in the area I live.