Universities only look at grade 12 courses (my school encourages us to try extra hard in grade 11 just in case.) Im not saying slack off or anything just don't stress about grade 9/10 classes. The most important thing to do in grade 9/10/11 classes is to keep your options as open as possibe. Its better to be getting a 60% in a university/academic class than it is to be getting 90% in college. And take all the science and math courses you can.
I as well have thought about vet school but like the others said its a big commintment, its harder than becoming a doctor because doctors only learn about one species you learn several. But you may love it. If you find after a couple years of highschool your not liking the sciences in may not be in your best intrest because you have to take all sciences.
Anywho, I have no problem balancing everything, just make the best of your class time. Lunch is also great too.
Yeah 11 you can pick I htink all of your subjects, or all but one.. I can't remember! And you generally have one less subject, so instead of 7 subjects a year, you do 6, and the spare lesson is a 'free' or 'supervised study' period. Use these frees!!!!!! My friends used to take off to the shopping centre, or go out buy fish and chips and lay out in the park for an hour. Use this free time wisely, study study study, get as much of your homework done as possible in this time and you'll feel so much better when you get home.
As Nirvana said, you may not enjoy the science topics and decide to take a different path. If you find you are struggling in science, maybe look into getting a tutor to help you out. But just remember that university science is going to be twice as hard as high school science, and in uni they don't hold your hand to guide you through it, you're on your own. That is another reason why I decided to change my courses, animal science/vet science/agricultural science all have an extremely stron focus on chemistry, and I did struggle through high school chemistry. I passed, but only just and needed to work very hard at it.
Environmental management also has chemistry, but not quite so full on as in the other courses. I love biology so wanted to pursue a science field, and am very happy with my decision.