Okay, first I think it is great if you are in HS and already looking into a law career. Shows initiative. I also think this site is good for you. But, I don't understand asking for advice about grades and college and stuff like that. I think most of your questions can be answered by your parents. Hell, I graduated from Ugrad last May and I still ask my mother for advice about law school (it helps that she is a lawyer).
People here often times like to trivialize your questions for whatever reason. I think the best thing you can do in HS is try to at least get a glimpse into the feild. If you know a lawyer, or more likely if your parents know lawyers, job shadow them for a day, you get to skip school, too, so it's doublely good. You can't know for sure that you are going to law school when it is so far away, but you should try to be informed. The more you learn, the more you will know (no sh*t, huh). If you still think you want to be a lawyer your senior year, start thinking about how your going to get yourself in the right position. What Ugrad you go to, how well you think you can do in a specific major are both important. But these are all generic topics, and you should be able to get advice from real-life people. I think you should use this board to get an idea about why you want to go to law school, and stuff like that. This particular board is pretty dead, so venture around and see what people are talking about, just don't be a troll. Oh, and once you turn 18, don't get in trouble with the law, it can f*ck you over for law school (just one of the reasons). There you go, take this for what it's worth.