I’d recommend you do honours maths and chemistry, regardless of what science you want to do in college. If you’re more interested in biology or physics, take those. If you like engineering, applied maths is handy (as is technical drawing/engineering).
I’d recommend reading around popular science books, see what catches your interest. I love reading these books on other aspects of science that I don’t study directly (eg. chemistry, Bright Earth by Phillip Ball and The Elements of Murder by John Emsley are great).