The long version:
Since high school students are always thinking about their ATAR, many often incorrectly assume that this is also what medical and dental schools think about. In reality, ATAR is just one of several assessments that medical and dental schools think are important—but since students have very little knowledge or experience in these other assessments, they can become overconfident about their chances of entry. Unfortunately, even if you achieve an absolutely top ATAR (e.g. 99.95), this isn’t going to get you into most medical or dental courses unless you also perform well in their other assessments, which assess very different things to the ATAR.
Generally speaking, most Australian medical and dental schools evaluate applicants on the basis of their UCAT score, interview score, and ATAR, with applicants needing to do well in all three to be considered for entry.
For example, out of the Australian medical and dental courses that hold interviews, almost half of them use the UCAT as the sole criterion for deciding who will get an interview offer, without considering your school grades at all—so without a good UCAT score, you might be eliminated at the very first hurdle, even if you’re on track to a 99.95 ATAR.
In fact, for courses like the Joint Medical Program (Newcastle & UNE) and the Joint Program in Medicine (WSU & CSU), your ATAR is only a threshold requirement: as long as applicants’ achieve an ATAR of 94.3 or 95.5 respectively, they set aside their ATAR and make their selection decisions purely on the basis of your UCAT results and performance at interview.
One of the universities that 99.95 ATAR students are often most shocked to be rejected from is James Cook University, since it does not require a UCAT result (or even an interview, if you’re applying to study dental surgery). Again, the reason why high-scoring students don’t make the cut is because the university isn’t just interested in your academic abilities, they also want to know that you have the traits they’re looking for—so when they review your written application, you’ll be eliminated if what you’ve written doesn’t adequately demonstrate this.
The short version:
If you really want to gain entry into medicine or dentistry, you need to be well-rounded and achieve high scores in all of the assessments, not just your ATAR.