I applied to CLA (I didn't take physics (long story), so I couldn't even try CSE) with a HS GPA of ~2.5-2.6 (2.99854 weighted, not that that matters) and an ACT score of 28. I gave so few fucks in high school. I'm still surprised that I got in. I'm 90% sure they only let me in on my extracurricular activities such as all the programming stuff I did instead of doing homework in junior high and high school. Also, I did FIRST Robotics for three years (programming captain). That probably helped too.

I also did IB in high school and may be getting an IB diploma, but I don't think the U gives a shit whether I get the IB diploma or not.

TL;DR: if you're good at shit and can show it, grades don't matter as much. That said, make sure you're actually good at shit. Don't just assume you are after a few people tell you.