In addition to the above, there are three factors that I believe you should consider when making a decision regarding which subject to drop. They are:
- Personal interest
- Performance
- Relevance to further study
Personal interest:
Consider your experience in both Physics and Legal Studies throughout year 11 and the time you have spent in year 12 so far. Which of these subjects would you consider to be more appealing or more consistent with your personal interests? It is important to prioritise subjects that you enjoy (or at least subjects that you do not despise) as those can make your HSC journey slightly more enjoyable, which leads to the possibility of superior performance, as opposed to having to take and endure a subject that you are not interested in for the whole of year 12.
Since you are taking Mathematics Extension 2, you should also consider whether the inclusion of Physics concepts in this subject may be relevant to your decision.
Performance:
This is also an important factor, as favourable performance across your subjects is (I assume) an ideal outcome for you, given that it will ultimately enable you to achieve your desired ATAR. Based on this, you should compare your performance in Physics to that in Legal Studies. If there is a significant difference in the level of performance between those subjects, then it would probably be best to drop the subject where your performance is inferior. This would also align with your academic goals in terms of maintaining the best possible subject combination for you, consequently increasing your chances of reaching your ATAR goal.
Relevance to further study:
If you intend to pursue study beyond the HSC (for example, a Bachelor's degree), you may wish to consider whether either Physics or Legal Studies are relevant to the degree(s) that you plan to study.
As far as I'm aware, knowledge gained in Legal Studies is not necessary if a student wishes to study a Bachelor of Laws. However, taking this subject results in a nice addition to the student's general knowledge in the sense that it can, to an extent, familiarise students with the basics of the Australian legal framework.
On the other hand, Physics may be considered assumed knowledge for degrees such as a Bachelor of Science (or similar). If Physics is relevant to a particular field of study that you are interested in, then you should probably keep it. If not, you should probably drop this subject (of course, that is after having considered the above reasons as well).
I hope this helps!