See if you wish you can join coaching classes but it isn't necessary. You should strengthen your fundamentals in 11th and 12th and you can join the coaching in the 1st year/starting of the 2nd year of your college. Most of the coaching institute design there courses for 2 years. Thus in this way you will complete the course by the end of your graduation. As a result you will save a lot of time compared to that of any other aspirant. But if you start taking coaching classes from 11th then you have to again get admitted for the course in your 2nd year of graduation. So its better for you to go for coaching classes from 1st year or starting of 2nd year of your UG course.

Some of the top IAS coaching institutes are:

• Rau's IAS Study Circle
• Chanakya IAS Academy
• Sathya IAS Academy
• Vajiram and Ravi's IAS Academy
• Drishti IAS

I hope this answer helps. All the very best for your future endeavors!