Most training providers in Australia are eligible for an edu.au domain. If you are an RTO you immediately are eligible, but many other training providers are also able to get these domains.
The main benefits of these domains is that they are trustworthy and get good Google SEO. That is, not only will students trust your organisation over one that is .com.au or org.au, but so will Google. That will rank you higher on search results.
They are cheap the the registration process is simple. Read more here Self-Assessment Guide
If you do change your domain, make sure you let Google know through the search console https://search.google.com/search-console/about and ask us at ish to ensure your old and new domains both work for your site. There is no cost for this.