I acknowledge that MBA students fresh out of undergrad
might have less to offer in the classroom... as I've said in prior discussions, I actually kinda like the fresh perspectives that younger students offer. In any event, the number of students without prior experience, even at H and S, remains quite low. I believe there are < 10 such students out of ~370 in Stanford's incoming class.
There's no doubt that the average age is starting to trend lower at H and S, though. I'm not sure of the reason. As pelihu mentioned above, B-schools may be trying to target students at an early age before they flow to other professional/grad schools. Makes sense, though I don't think they're going to get many people who were thinking about med school. The required pre-med curriculum is quite clearly defined and the MCAT is a major pain in the a##. You either commit to the medicine route fully or you don't pursue it.
There may be something to gaining more female applicants by recruiting at a younger age, and that seems laudable. As has also been mentioned, all of this may have arisen from the desires of consulting firms, banks, and PE firms to have younger and more obedient associate-level employees.
In summary, I have no idea
p.s. Out of curiosity, TFN, you mention that "60% of graduates go into investment banking, consulting, and private equity" at HSW. Did you get this info from employment/recruitment reports?