I don't know how it works in Europe, but I can tell you that here in Canada, high school is really not as big a deal as your teachers make it out to be. Study as best as you can, and if you screw up really badly - well, I don't know how the school system there works, but at worst you can always repeat a year, right? Anyway, if you want to do well, pursue what you're interested in.
The kids that do really well in a class are the kids who the coursework resonates with. We live in a big world. There's a lot out there, so there's got to be something you'll excel at. You'll find your niche.
(We don't even have SATs here. Our Universities accept us based on our top six high school grades.)