Lots of math--up through calculus, chemistry, physics, biology, anatomy and physiology, speech, and psychology. You will be taking these same types of courses at a more advanced level in college. The more you take of these in high school, the less time you will have to take doing lower level science in college to get to the more advanced work. If you take the time to look at what pharmacy schools want you to have under your belt from the lower division college level, you will see what type of skills they want you to have. Typically, pharm schools accept more people who have a bachelor's degree in some type of science, such as chemistry, biochemistry or pharmacological chemistry. Those folks are more competitive.
Again, just google any of the pharmacy schools you have in mind. Look at their admissions requirements. Some will also want you to take an entrance exam that shows how much you know about the sciences and math and problem solving. So, understand that not only are strong grades necessary but the scientific skills you have acquired, along with the ability to understand and deal with the public.