I'm currently in my junior year of high school and looking back, my grades have been just average, if not lower.

Yeah. So is mostly everyone, hence, "average".

Will this affect me in my future pursuing a career in CS?

No, but this: "but I am very lazy with things I am uninterested" will.

You will dive into some fuck-ugly code, write some boring useless crap, and hate it. Even those "rockstar" programmers that get hired at those sexy companies do boring work.

Seniors get to have all of the fun.

Is it possible to still have a stable well paying job in CS?

Yes.

I am very passionate about computer science and I consider myself to be ahead of many of my colleagues (I don't want to seem cocky).

No.

You are ahead of your "colleagues" because they don't write code in their spare time. You will have a slight advantage come college, but, unless you're truly some wizard, it evens out.

It's like getting really tall, really, really early. Yeah, sure, you're the first kid to be 5'10, but then once you're 22, so are a ton of other people.

You'll breeze through your intro class, make fun of the other 'idiots' (who are taking it for their first time), and then you'll get to your data structures class, with those same idiots, and you'll all feel like you've found yourselves in uncharted territory.

I am telling you this because I was the same way.

I fucked up badly in high school for a lot of reasons, but mainly because I was some weird, egotistical introvert who thought I was above everyone else because I could write some poopy Java and basic, basic webdev stuff.

All of the actual intelligent people ended up doing well, going off to great schools anyways, and even surpassing me because I ended up having to go to community college because I fucked up so badly.

Granted, I still ended up managing to transfer somewhere nice, but, It's been an interesting ride.

Learn good habits, and get over yourself (in a blunt, kind way), and you'll be great.