First, set up a schedule for yourself. Calculate how many hours you will be spending getting to practice, practicing, and at games. Make sure that you can handle both your academics and your sports schedule.
Now, calculate how many hours you should study while in high school. No it is not zero! LOL. You then test it out. Try studying 2 hours per week for every class. If you have 6 classes, your study time should be 12 hours. That could be 1 ½ hours per day/night and the remaining 4 ½ hours done throughout the weekend.
Does this work for you? If your goals are A’s and it is not enough, adjust it. If your study time is too much, keep it the same. You can always work ahead, on prep tests, upcoming college research, upcoming scholarship applications, etc.
You just have to plan a system and then work the plan. After all, this is what you do with your sports, work your academics the same way!