I knew a few couples in college who were doing this. They wore rings and explained that it was an education-related decision. In one case the woman was a year behind and in another he needed an extra semester for a large major. It was hard for them, but people seemed to accept it. If you're still a young couple, people seem to think a proper education is a good reason for most things.
Like everyone (especially newlyweds), you'll probably have people ask you your share of tactless or painful questions (as well as the fine ones). I've got various short "end of conversation" answers about why we don't have children yet, when we are, etc. One way to turn it off the subject might be to mention what she's studying, how she's almost done (hence no transfer), etc.