If your son is not PR, then none of the above schools will be open to him I wouldn't think.
Do you know about enrolment phases for foreigners? In a nutshell, local kids get placed in schools and the leftover places are available for foreign kids. Not always a bad thing, since the idea of "good education" in Western countries differs a lot to that of the pushy and high-pressure top schools here. The government is working on changing this and the changes seem to happen first in the lower rank schools where parents, staff and students are more open to change.
It is worth considering putting your son in a local school to start off with. The move to an
International School would be easier than a move over to a local school if it turns out to be a very expensive exercise.
All the
International Schools here are excellent, so choosing one will really depend on what you want and what will suit your child.