I had been under the impression that enlistees like Chief O'Brien did not attend Starfleet Academy, but I was just watching DS9 episode "Trials and Tribble-ations," and Dr. Bashir made the following comment:
Come on, Chief, surely you took elementary temporal mechanics at the Academy?
Being close friends by this point in the series, Bashir would certainly know whether or not O'Brien went to Starfleet Academy. So it seems to me, this leaves one of the following options:
A. Enlistees go to the Academy as well, but for whatever reason don't get to be officers. Maybe poor grades, or an abbreviated courseload for enlistees?
B. Chief O'Brien failed out of the Academy and decided to enlist instead.
C. There's some other Academy to which Bashir is referring.
D. This is a scriptwriting error.
D seems like an unacceptable answer because, even if this were the case, the mistake should be rectified by working it into the lore. C would make sense but if so, you would think it would be mentioned at some other point in the history of Star Trek. That leaves A and B, which both seem equally plausible to me. Or is there another option that I'm overlooking?