My family are moving to Australia but I want stay in the UK to finish my education first.

Once my family have activated their visa, they will be moving over to Australia within the next 5 years and I want to stay in the UK to finish my education over the next 2 years and then I want to join my family in Australia. But I will be 18 in 12 months and want to know if I will still be on the family visa or will I need to apply for my own? If so, how do I go about this and how long will it take?