Is Coaching necessary to crack IIt-JEE or AIEEE exams?

I'm already 2 weeks into 11th grade(CBSE) and i can't make up my mind whether i should join coaching classes or not..I got A1 grade in my 10th board... I really want to score good marks in my 12th boards and crack IIt-Jee exam.. Will attending these classes help me to crack IIt jee.?? Please advise..