Dear Saiganeshgona,

You can write competitive exam after completing your 12th class. 

You have enough time to prepare for the exam so utilize it to get better results. 

If you are planning to get into IITs there is a lot of competition as it is a dream of many students. 

You need to plan your studies make your time table which will help you to complete your course.

11th class is very important to build your basics so make sure you make your concepts clear.

All the Best!!