The way it works for a great many teachers I deal with is that they first of all get up the courage to invite an Indigenous speaker into the school. This seems to happen a lot with the Aboriginal Studies component of the Australian Studies course at Year 11 (or in some schools at Year 10), or at other levels when teachers are told that they need to 'teach Aboriginal studies'.
This is in itself a bit of a challenge in that many teachers have never spoken to an Aboriginal person before, and have no idea how or who to approach one to ask them to talk to a group of students. (This is where it is very useful to have some knowledge of local community people, gallery staff, Indigenous organisations or an Adviser to ask for a lead!)
The teacher suddenly realises that there is a whole group of articulate, experienced and successful, as well as appallingly treated (this usually comes out in the session with students) people that he or she knows very little about and with whom we share a country which was, not so long ago, theirs.
This is often such a powerfully engaging experience that they get the confidence to suggest that other colleagues might do the same thing, and then to start thinking about what else such a person could contribute to the school.
He or she is usually confronted, and disturbed, by the depths of their own ignorance. Most people decide to take steps to correct this. Teachers don't like being ignorant wilfully. The teacher then tends to search for ways of meeting this need for their own knowledge by enrolling in PD sessions (if they are offered and the teacher knows about them, and the school will release them) and doing some reading.
Once the teacher's perspective changes, they also realise that they actually need to know more so that they can develop more appropriate curriculum responses, that the students need to know more about the facts, and the teacher needs to be teaching Indigenous perspectives and incorporating these into the curriculum. So curriculum change follows.
In making these changes, the teacher will come up against the reality that the school probably has few useful and appropriate resources. They often take on working for this area to be better resourced. This, then, can often lead to a greater awareness of the whole school perspective (or lack of it) in terms of Indigenous issues. And this, for many schools, is the start of the questioning and challenging that leads to changes in school policies, practices and priorities. (Education Departments have a lead on this, as they at least have policies, even if they are not always implemented.)
He or she sets up a small group in the school which, over time, becomes formalised because there are so many sources telling us that this is what must be done. This group gains some influence with the school leadership which is generally willing to go along. And there you've got a change that usually matters.
This process can be triggered by the enrolment of one student. In terms of the process, it doesn't matter how many students you have, except that, when there is a critical mass, ie, from no students to something like four or five, then it is often given more attention by management and things move more quickly.
However, it is always, I think, at the single teacher level where change starts and, eventually, produces a real result.