This is a super interesting question for those in high school: What do you need to focus on in high school?

I'm not studying Computer Science and finally realised the framework that worked for me and probably will work for you too.

You need split your time outside the school into three parts:

1) Foundation: This part should take 30% of your time. You need to learn and understand everything that they teach you in school. This means to get very good grades.

2) Learn your craft: This should take 50% of your time and is the most important. Become great at a subject of your choice.

3) Understand the world: This should take 20% of your time. Its scope is to widen your horizon and perception of the world.