hey there!

You can surely get good marks inn JEE only with NCErt knowledge provided you study it deeply the concepts and fundamentals. But it is wise for you to follow a coaching pattern for better results.

NCERT is the syllabus prescribed for JEE.

But Since JEE is a competitive objective type exam the questions are made tricky and of a different approach. The application of the theoretical concepts is done in the paper.

So , study NCERT also go for some JEE based books and refer previous years question papers for more idea on it