Hii, i will help you according to your query.CAT according to the definition of average is 50 Percentile. A student with 50 %ile in CAT is most likely not getting a call from IIM Calcutta for an interview. So, an average student (consistently average student) cannot make it to IIM Calcutta.If you already scored ur 10th, 12th, and Grade academics chances of making it to IIMs is difficult. But then, 15% of the batch at IIM Calcutta are exceptions. But how can a set of 60 students be called ‘exception’? You get the point!All the 6 pointers at IIM Calcutta cracked an exam called CAT. Probably excelled during the Personal Interview. 

Hope,this information will helpful for you.Goodluck.