Business schools offer places to people from many different walks of life. Business/work experience would be a consideration but so is the GMAT (an entry test), the interview, and other qualifications. DM is first and foremost a research firm to my mind, and as such there is some overlap with some areas of consulting, but it is not a pure consulting firm. However whether you come from a big consulting background, or not, is not a key determinant of getting a place at business school. It helps but so do other experiences. I've done work with DM in the past and like them. I imagine it could be quite a fun place to work, and you would certainly get good exposure to the business world - and actually understand a fair bit about it. Pay might feel a bit stretched there after a few years (others might disagree), but it would offer you a solid basis for your career path.