I did a foreign mba, from a top 20 school.

of course, if you are able to get into a top school like insead or wharton, it boosts your chances even more than my top 20 school, as their career services offices are even stronger.

Also, all banks will have their 'key recruitment' schools, where there's a certain no of allocated seats. For eg, a bank may want to recruit 100 MBA grads for their annual management associate programme. So assume the bank has 4 'key recruitment schools', each with 20 allocated seats, that means that 80 seats (4 X 20) are accounted for and they will only take in a total of 20 people (100 - 80) from the thousands of other MBA schools globally. That's why its so hard to get in if you are not in one of the 'key recruitment schools'.