This can happen anywhere. I remember my old high school math teacher helping the star math pupil get a higher score on the AIME[1] and then again on the IMO[2]. The student was suspected of cheating and, thankfully, given a second chance to take the exam again (don't remember which one) without the teacher present.

[1] http://en.wikipedia.org/wiki/American_Invitational_Mathemati... [2] http://en.wikipedia.org/wiki/International_Mathematical_Olym...