If you're actually looking for a reason (if undoubtedly not all the reasons, of course*), you might check out the
employment rate. (2010 numbers... would be interesting to see what latest numbers are, but that's close enough, really.**) It's not uncommon for folks that can't get work to go back to school, and when there's a pretty noticeable gap between male and female employment rates, well...
And to preempt it, no, you (general you, to everyone) don't want to be looking at unemployment in this case. Unemployed is a specific thing which leaves out quite a bit of the picture. What you particularly want to compare is the labor force and not in labor force numbers; that would include the total employment numbers and the folks who are not currently looking for work but
are, say, going through training. Also nets in stay-at-home folks, but yeah.
60-40 split starts looking a bit less unsurprising when you see a 58-70 split going the other direction. Less males in school because, hey, they don't need it quite as much.
If you want a more detailed picture, you could check the data
here. Bounce back and forth between the male and female data sets, particularly in relation to total numbers in the workforce vs. total numbers at varying levels of education. What holds true across nearly all of them (with the only exception being at the doctoral level, and then by less than a percent?)? A higher percentile of males end up working, when compared to the total number of individuals who obtain that particular level of education. Interesting bit: You don't really start seeing a noticeable gap close until you start getting into masters+, and even then there's a ~10% difference between professional degree holders in the workforce (though only ~4% in masters and, as noted, <1% in female favor with doctorates). You want to account for stay at home stuff, compare across 'not in labor force'. At least at first glance, no, the numbers wouldn't explain the difference.
Now, can solid conclusions be drawn from that? Well, about as solid as those drawn from the difference in college enrollment, hrm.
*As with all this kinda' shit, multivariate problem is multivariate like
goddamn.
**Actually, they've got the 2012 numbers up, silly me. Let's take a gander... E: Looks like the trend's mostly exaggerated. Women now have a notable lead in doctoral job acquirement, have closed the gap a bit on professional level, and made some gains in the some college bracket, but are otherwise worse off.