Hi,
The best time to start preparation for IITJEE is class 9th. You are under no pressure then, hence you can go steadily on your path of completing the course. You may also join Askiitians.com's Foundation Course for Class 9th and 10th students, wher we prepare them, making them masters of concepts that are asked in IIT JEE.;
Thanks and Regards
Rajat
Askiitians Expert