Hmmm. I never thought about that but you're right, it doesn't make sense for an Orion to be enrolled in Starfleet academy. The biggest problems I had with the movie from a canon standpoint was they made Chekov a Weasley Crusher style 17 year old "boy genius", who was nothing like Koenig's Chekov (in TOS, it was clearly stated on screen that Chekov was 21, so since the movie was set 8 years before TOS, Chekov would be 13 at the most). As for the "Star Wars" influence, the scene with the phaser fight aboard the Romulan vessel was way off. Star Trek phasers operate completely differetly in established canon. It was like Kirk and Spock beamed onto the ship with some Star Wars ray guns. At least they didn't give them lightsabers.
Add to that, the problems with having an Orion girl in close proximity to any males at the academy and you’d have a bad situation on your hands. They should’ve substituted a Deltan female (a la Ilia from ST:TMP), who is as sexually powerful as an Orion slave girl, but can strictly control their libido (note Ilia’s line in the film that she took an “oath of celibacy”, lest she drive the males nuts). Of course, not a lot of actresses can pull off the bald look and still be hot as the late Persis Khambatta could (though she looked much better with her beautiful black hair).