To get an idea of what law school exam questions might look like, I recommend you get a copy of a "Gilbert Law Review" book. They make them for different subjects. I have one on Evidence that is pretty interesting, and another one on "Civil Procedure." At the back of the book, they give you questions to work on. They are very complex questions.
You have to approach the question methodically, with a whole checklist of questions. So, they might give you a situation: A customer spills his drink in a club, slips on it, bangs his head, and requires medical care. He then wants to sue the club. Initially, you think, gee, it's his own fault. He spilled the drink. But you have to ask, "what caused him to spill the drink?" "What did he bang his head on?" etc. etc. etc.
The books are very thorough. I just looked and found one on Constitutional Law, selling for $20 - $40. A good library should also have them. There are many topics: Contracts, Business Law, Torts, Immigration Law, Family Law, Wills & Probate, Criminal Law, etc.
Because you are so young, once you have looked at these books, I'd recommend focusing on preparing for the LSAT - the Law School Admissions Test. It is also very intense. There is a whole section referred to as the Logic Games. If you do not know how to solve these problems, you will not have time to try to figure them out. One example: Mary, John, and Sue went to a concert. One of them was wearing a red shirt. The one who was wearing a baseball cap was wearing a blue shirt. John took a taxi. The one who took a bus was not wearing a baseball cap. . . . (that's not the whole problem, just an example. You have to figure out who is wearing what color of shirt, and what transportation they used to get to the concert.) There are study guides available to help you, and actual classes you can take to prepare for it.