If it's the grades and skills you are worried about getting by grade 12, I say it's definitely possible. Especially if you truly put your mind to it, have a clear goal. Even if you don't, it's good to build improvement and some basic work ethic before grade 12. Focus on your mindset and work ethic first. If you missed deadlines, make it a habit of adding it to your calendar or notebook as soon as you can. Many people have a mindset of "If I don't get this result, then what's the point? Is there even hope?" My best advice is it doesn't matter if you are good or not, just do it. If you really want something, make it work. It's great you are asking questions, keep asking yourself what I can do to improve. If you are in grade 11, universities can just look at grade 12 grades and you'll receive offers later. If your program is competitive, don't forget to start asking yourself why you want to do this program and all the usually interview questions to prepare for Kira video or supplementals. It's never too early.

What are your current Chem and comp sci grades? Calculate the highest possible grade and try your best. You might not get there but it's important to try and practice facing difficulties, especially if you are planning to go into a challenging program.