None, really.
Law school is a graduate-level school, so that means you have to go through a four-year university first. Thus, no law school is going to look at your highschool transcript.
That said, you'll probably want to take as many A.P courses as you can in a variety of fields (A.P European History and A.P English Literature are great at sharpening your critical thinking skills).
That way, you can apply to better undergraduate colleges (and be better prepared for them) so that you can eventually move on to better law schools.