I was really good with math from year 9 to 11 but in year 11 I had a passing in my family and decided to drop to standard math and English as I could not cope. Is it possible for me to still do computer science as someone who did standard math?
Standard math should be okay. Depending on the syllabus you may need to improve, your knowledge.
Let say you are doing subject called mathematical modelling 1 at UTS (I recommend looking at the UTS handbook). Then the failure rate would be about 50%.
To deal with this you would need to study calculus. You can do this using any standard Advanced Mathematics high school textbook or university textbook that goes over calculus.
James Stewart Calculus: Concepts & Context should be good. However cover some content outside standard highschool maths class. There is also a solution manual or odd numbered exercises in book. In case you have any trouble understanding something you can always search on math stackexchange.
Although you have not mentioned it if you have not done any programming before that could cause potential issues. I recommend taking 1-2 Udemy courses.