Groundhog is correct I have never heard of any law school looking at your high school transcripts. Your best bet is to get a high GPA at whatever accredited University you attend. Most law schools will simlpy care only about your undergrad GPA and if you get a 4.0 from X State opposed to a 3.4 from Semi More Respectable Private University X the 4.0 from X State will have more success getting admitted to law school.
The name of your Undergrad will make a difference if it is Harvard, Yale, maybe even UCLA, USC something of that caliber, but for the most part people have no idea what 90% of universities are doing or whatever proposed quality difference there is.
Also as GroundHog suggests it is probably to early to really be thinking about law school. Go to a university you enjoy, choose a major you enjoy, etc. You are only in high school and a lot of things can change I personally never in a million years that I would ever go to law school when I was in high school and now I am a lawyer. I know plenty of people in high school convinced they would go to law school and ended up succeeding in very different fields.
Finally when you go to College a lot will change it is good to have a goal like law school, but keep your options at least for the first year or two as your goals may change.