Excerpt from WSP's Ace the IB Interview Guide

I see that you have a 2.8 GPA.  Typically, we hire 3.5 and above.  What’s going on?
The GPA question – a great lead question for students on the summa cum laude track and a nightmare-inducing question for students who party/partied a little too hard.  The unfortunate reality of the financial world is that academics play a key role in resume selection.  The nice thing about getting this question in an interview for both good/bad GPA candidates is that the recruiter felt you were good enough to move you past the initial resume screen.  For poor GPA candidates, you clearly got the interview because of other things on your resume.  This is a good thing to know because you can better strategize your answer.   When answering this question, you want to be cautious about what you say.  You don’t want to spill your guts out and say that you were at the bar Saturday through Thursday and class just on Friday, but you also don’t want to give the impression that you are academically struggling and can’t handle the coursework at your university.

Poor answer
Poor answers to this question include ones that paint you as one of the main characters from Animal House.  It is ok to tell interviewers that you like socializing and having fun with your friends on weekends, but I wouldn’t focus/bring drinking into the question.  Tame your answer down and take the more “conservative” approach.  To say that you go out with friends for dinner and drinks (only if you are 21 and over…be very careful about this as your interviewer may be testing you) is much better than saying you play beer pong from 1pm – 8pm and then hit the bars until close.  Interviewers were once college students and know what actually goes on, but this question is also testing if you know how to sensor your answers in case they decide to put you in front of a client.  On the flip side, if you were one of those that lived in the library and simply are not good test takers and thus don’t get good grades, do not also spill all your beans.  At the end of the day, investment banking/finance is a knowledge industry.  Many of the best and brightest from the most prestigious universities in the world enter the field.  Your interviewer wants to know if you can handle the analytical component and you don’t want to give them the impression that you can’t.

Great answer
Great answers to this question include ones that provide justifiable reasons why you are not performing.  For example, if you have above a 3.5 every semester, but a 1.0 in 1 semester because of family issues (i.e., death of a family member, etc.) mention this.  Everyone goes through hardship at some point in their life and unfortunately for you it happened in college.  If this is the case, illustrate this on your resume.  Show your GPA with all semesters but the bad one and then your cumulative GPA.  If you are active on campus (i.e., student government, active in many clubs, varsity athlete, community service coordinator, etc.) or are working as a full-time student and you were either a partier or bad test taker, craft an answer that pretty much says you were very busy with extracurricular activities and given your difficult coursework and commitment to extracurricular activities, it is difficult to balance both.  In such a response, while you are taking ownership of your GPA, you are also helping your candidacy by showing how active you are outside of class.  This last response is typically the best approach.

Sample great answer

“Frankly, I made some bad decisions as a freshman which I have been able to partially reverse through a lot of hard work over the last few years.  My very 1^st semester at Notre Dame I did not manage my time well between extracurricular activities and academics and received a 1.8.  After reflecting on my poor performance that semester, I realized that I needed to get my priorities in order and started to focus more of my energy on my academics.  Excluding that first semester, my GPA would have been 3.5. In fact, I have continued to improve every year and over the last year I have maintained a 3.8 GPA.”