You have a temporary hurdle to jump over. Get good grades. The aim of getting good grades is only to get good grades. There's a bunch of stuff that you can do with good grades, and if that motivates you it's great. But at the moment you just need to get the good grades.
So, perhaps when you're studying you put in 30 minutes for school work, and 15 minutes for what you enjoy, then have a break. Then repeat that.
This allows you to get the good grades, and keeps you interested in the subject.
You'll have a bit more freedom in Uni, and you'll so you can see your current task (get good grades) as also being "learn some discipline".
There will be some people who want to get better grades than you. Thus, you should get best grades you can just to stick one in the eye of those people.
This is very good advice. If you get nothing else out of high school, make sure you learn the discipline it takes to study something that's not immediately rewarding. Not only is it important right now in order to have choices for the immediate future, it's a skill that will serve you well throughout life.
Working for good grades caused me to get burnt out on school. What has motivated me to learn more than anything has been due to being engrossed by the value of the learnings application. If you can be motivated by increasing a grade letter, more power to you. But I argue that a student focused on a grade is going to get less out of the education than someone fixated on a subject for its own merit.
So, perhaps when you're studying you put in 30 minutes for school work, and 15 minutes for what you enjoy, then have a break. Then repeat that.
This allows you to get the good grades, and keeps you interested in the subject.
You'll have a bit more freedom in Uni, and you'll so you can see your current task (get good grades) as also being "learn some discipline".
There will be some people who want to get better grades than you. Thus, you should get best grades you can just to stick one in the eye of those people.