I have always been totally dependent on my parents 'cause I hav no other sources to depend on, although full time education is not mentioned on Aus Immi Website as a criteria to add dependent child, I decided to keep my full time education till the visa be assessed to get the best chance possible, you can see here:
To include a dependent child in your visa application, the child must be:
your child
a stepchild from a current or a previous relationship (in certain circumstances).
Acceptable documents that can show a parent-child relationship include:
a certified copy of each child's birth certificate
a certified copy of adoption papers.
Your child or stepchild is considered to be dependent if any of the following apply:
they are younger than 18 years of age
they have turned 18 years of age and continue to be wholly or substantially reliant on you for their basic needs (food, clothing and shelter)
they have a mental or physical disability that stops them from earning a living to support themselves (whether or not they migrate with the applicant). The child can be of any age. The child will still need to meet Australia’s health requirement.
A child of any age is not considered to be dependent if they are currently married, engaged to be married or in a de facto relationship.
Some visas require that the child has never been married or in a de facto relationship.