Hello Applicant,

Your X and XII marks are going to be considered every place on this earth, irrespective of whichever college you apply (Top B-schools). That will play prime criteria in your selection to the college. IIMs are more so known for doing that specifically. 

Extracurricular courses are an added bonus. If it is there on your resume, that will draw the attention of the interview panel. But that won't play the sole criteria of your selection. In short, if someone has very poor academics and extraordinary extracurricular achievements, there are chances of rejection because they look for balanced profiles.

Ultimately you will be competing with people who will have better academics and will anyway be preferred over people with poor or below average academics. 

Hope this helps.