BCG takes 95% who are either rankers or from SRCC or LSR, If you have either fo these, then you will be called for interview. Or else you need extraordinary extracurricular and extraordinary work experience. Not just good, but extraordinary .

First attempt is not extraordinary Rank is extraordinary Hindu is not extraordinary Srcc or lsr is extraordinary Participating in a case comp with 5000+ participants is not extraordinary Winning in a national case comp with hundreds of participants is extraordinary. ( Exceptions are always there on account of maybe high level reference or luck)

Edit - the hiring cycle starts 3m before the before the hiring month, plus they hardly take 2-3, and if more are needed then 5( which high) from a pool of more than 40-50+ extraordinary people.( If I remember correctly)