Game Design Pathways
If you are interested in pursuing game design after high school, check out my Game Design Pathways page for other classes you can take to hone your game design skills. They page also has information about Unity certifications that you can pursue.
Unity Certifications
Unity has a number of certifications that you can get, some even possible while you are in high school. Here is the link to the Unity Certifications page. If you more into the programming side of game design, consider the Programming Certification. If you are more into the artistic side of game design, look into the Artist Certification. Unity has three levels to their certifications: User, Associate, and Professional. In high school, you would shoot for the User level. Associate and Professional levels are for people who have published their games and are making money on them.