What to expect in a high school?

Even if you go to a fancy college prep high school, in the end all that does is help get your foot in the door; your GPA in high school doesn't affect anything other than ability to get into college, and even then you can bypass the need for good grades with an incredibly high score on SAT/ACT/whatever you have there. So, while you can stress out over grades, they technically only really matter in college, so it's better to just do things in a balanced manner. No reason to ostracize yourself from the rest by constantly studying instead of hanging out with them. Though, that's not what I did, I preferred reading, which is an acceptable option too, as long as it's something other than constant schoolwork.