I did very well through high school and am on track to do pretty well at university (British that is, none of your silly numeric grading for me!)
However, the grades you receive in high school literally only matter to get you into university. After that no one cares. I'm job hunting right now and apart from certain careers like teaching, no one actually wants to know what my high school grades were, they only want to know either if I've finished uni, or what I'm supposed to be getting when I finish uni.
So I'm sort of mixed on the whole thing. If you don't get into a good uni then obviously things won't look as good on your CV, and getting into a good uni requires good high school grades (mostly) but on the other hand I know people who got into good unis without excellent high school grades, and people who got incredible high school grades who didn't get into good unis, so the system as far as I can see is totally broken.