It is important to choose your core classes wisely. They are the best indicators of your academic potential in college. It is beneficial to take four years of all subjects to ensure your mastery in each of the core areas. However, The level you take the classes to is more important. This is why it is imperative that you start early in your high school career to take advanced classes, since those choices follow you to the last year of high school. Your senior year schedule is important to show where you will be when you graduate from high school. You should take the highest levels you are eligible to take and make sure you do well in those classes.
You need to ensure that you balance the difficulty of your core classes well. Do not look at each class individually, but instead look at your schedule holistically. It is best not to take many hard classes and then do poorly in all of them. You should also not take an extremely easy schedule just to secure a high GPA, as that does not show your ability to take a challenge. The ultimate goal is to challenge yourself and win.
The language classes you take are also important, as many colleges require some type of language experience to graduate. Often, if you pursue high levels of a language in high school they will exempt you from that requirement in college. It is better to take the same language all four years than to take different languages every year. If you speak another language at home, you should take a third language at school to learn a language other than your native tongue.