As far as I am aware, following the written application, the criteria for the UNSW Co-op Program include a certain ATAR requirement in addition to favourable performance in an interview with academics and representatives from sponsor companies. Students selected at the interview stage will receive a conditional offer that is pending until ATARs and cut-offs are released. Converting the conditional offer to an unconditional one therefore depends on whether students meet the specified cut-off. Because this program considers students' ATARs as their measure of academic performance, it is implied that year 11 results are not considered as part of their application.
The notion of high school leavers indeed refers to students who have completed their HSC. This is simply because students who decide to end their schooling once they complete year 10 are not eligible to apply for a Bachelor's degree until they complete an alternative form of education that makes them eligible to do so, such as a diploma. On the other hand, year 12 students who have completed their HSC can apply for a Bachelor's degree. In most cases, that would be on the basis of their ATAR. However, some may also be admitted solely based on the fact that they completed year 12, which is more common for smaller/lower-ranked universities/institutions.
In terms of advice, the fact that you have signed up for programming courses and competitions indicates your passion for computer science, which you can use to your advantage in an interview setting by making references to such initiatives in response to interview questions, where relevant. You may wish to use the following questions as part of your preparations:
- Why do want to study your chosen degree?
- Why did you specifically opt for a cooperative education program?
- How do you intend to use this educational opportunity beyond university?
- What are your expectations as a future student studying the Co-op Program?
- Do you have a strategy to maximise your learning and ensure favourable performance?
- What does school mean to you?
- Tell me about a time when you did something good for your school.
- Are you involved in your local community?
- Why would you dedicate additional time towards contributing to your school and/or local community?
- Tell me about a lesson that you have learned during your time in your final year of school. How do you intend to apply it going forward?
- Tell me about yourself.
- Tell me about a time when you faced a problem and how you addressed it.
- What makes you a good leader?
- Do you prefer completing tasks individually or working in teams?
- What can you tell me about communication?
- Why do you believe that you will be able to enter your desired profession?
Other than this, maximising your chances will require you to do your utmost to achieve the highest possible ATAR, which will hopefully exceed the cut-off that UNSW specifies and hopefully allow you to receive an unconditional offer.
I hope this helps!