My two cents is think in terms of type of school and not major. There are many undergraduate schools in the US (not so much elsewhere) that encourage a lot of exploration before committing to a major, usually not until the end of your second year. This could be an entire college, or it could be a subdivision of a college (usually called something like Arts and Sciences). This includes many of the most famous colleges in the United States, but also many more.
People end up going from such schools into all sorts of careers–law is one possibility, but also all sorts of different careers in business, finance, health professions, government, education, academia, media, and on and on. You never know what you will like, what you will learn from internships and such, and so on.
As others said, no one in 9th grade needs to be preparing specifically for this. Actually, more the opposite. These sorts of people are often high valued because they have a great range of basic skills, healthy habits, are social and good team players, and so on.
So, a 9th grader just needs to focus on healthy, well-balanced personal development. Academically, you should follow what is normally called a college prep curriculum, which basically means taking all the core subjects through at least three years and possibly all through four. Reasonably challenging yourself in terms of course tracks, depending on interests and abilities, is also a good idea.
But frankly, the vast majority of possible majors in college really have little or no high school equivalent. So, just develop your critical reading, analytic writing, math skills, scientific knowledge, understanding of history and cultures, a language . . . these are the core college prep subjects in the US precisely for this purpose, that a person who does all that will be well-prepared for this sort of US college experience.