Hello Reethika, 

You have to wait until the classes start because you won't know the subject and syllabus and niw talking about the 80 percentile then you can easily score that with regular practice when your college starts. Still if you want to start studying then i will suggest you to go through 10+2 course because the 1st sem contains same concepts.

I hope you will find my answer helpful. 

All the best.