Depends, what it is you want to do?? Work as a civil servant directly for NASA, or just work for an aerospace vendor that has a NASA contract? Do you want to fly for NASA, or just work on projects (spaceflight hardware, etc.)?
At Goddard Space Flight Center, I can tell you that the current Director of Flight Projects (my boss's boss) was in the 3rd class of females that went to the USAFA, the Director of Management Operations was a pilot from the USAFA, and a good friend of mine in our Directorate was USNA and was a NFO on P-3s. Those are three that I directly know and have worked with, but I'm sure there are a ton more.
There are a lot of priors both as civil servants and contractors. It all depends on what it is you want for a job!