First, it's not an amendment. It is included in the original document.
All religions who wish to have access to the period of religious instruction. In primary school I would have attended Methodist scripture because I was baptised in that church. I attended Baptist Sunday School because it was the nearest church and was in walking distance. In secondary school I scripture shopped - Church of England to be with my best friend them Methodist or Presbyterian if the teacher wasn't crazy and could provide an interesting talk. Finally I opted out completely and spent the time doing extra chemistry prac work in the school lab. This was not allowed but our teacher did not chase us out.
Kids who were Jewish or very small denominations were usually unable to receive special religious instruction (SRE) in a public school for lack of volunteers. They went to the library instead. Other states have variations on this arrangement but there is a strong push from parents to do away with the scripture period. It is not compulsory for their children to attend but it is an opt out system and they feel that their children are being singled out and made to feel different if they refuse permission for them to attend.
To answer your other question, Rabbis, Imans, Salvation Army, Buddhists are all welcome to provide religious instruction if there are any children of that faith in the school.
I should also add that the school curriculum has some general religious education (GRE) which all students study. This is more like comparative religion and is linked to the history of Australia via the Human Society and its Environment strand. The regular class room teachers deal with this section. It is about religion rather than being religious in nature. The students would learn about major religious festivals Easter, Christmas, Ramadan, Hannakuh, Divali etc and the Aboriginal Dreamtime and the significance of sacred sites and song lines. The purpose is to promote understanding of how religions affect society and to develop tolerance for difference.