FJ if you go to your GP you can get a referral to a pediatrician and the ball will roll rather quickly from there. The first couple of visits are quite intense as there is a lot of questioning and testing. It is also a bit costly but it does to toward the safety net. I understand how hard it can be at home and frustrating when they don't act the same way at school.

Hi Tania and welcome At kinder here (could be different in SA...) they have what is called a Field Officer who looks after the region and is support for the teachers. They are also more trained to spot issues in the kids that might need help. As a first step you could ask the kinder teacher if there is some kind of support available for him to be watched in the kinder environment and request that they do so. Ask the teacher to write a report of the things that could be potential issues also and then you can take that to a pediatrician also.
As Masons diagnosis was made through the kinder year that was how it was started for us.