if ur goin to prepare of iit-jee  than board course is like a drop in a ocean..

in coaching centres teacher help u to solve high level problems...at times some chapter r neglected or given less important in iits.....so these chapters u have to cover your self..bt they r nt that difficult that u have to take seprate coaching for that.....do rem u have to manage time..which is going to be the most imp factor... i have seen few students who join so many coachings bt couldn't make it to any thing...

P.S: self study is key to success