I am assuming you to be a pcm student because you haven’t mentioned anything, so first and foremost point, will be to try and clear all your concepts from ncert book(exept Physics) and then go for the books I am mentioning below:
PHYSICS: SL ARORA( ample amount of numericals and good theory)
Chemistry: only Ncert and ncert exemplar
Maths: ML Agarwal
English: Full marks
And you must solve the previous 10 year paper of all the subjects before appearing for your boards. This will definitely land you to a 95+ overall percentage for sure
Good luck