From the episode "Blank Stare Part 2". Principal Blackman forces a girl to take her shirt off because of religious symbolism. "But, I'm not wearing a bra!", she tries to protest, but to no avail. The camera pans away just as she embarrassedly begins to remove her shirt. You can see her pokey nipples, so she really wasn't wearing a bra.
Later in the scene (not included in the video) you can see some extras in the hall staring in her direction. Guess they were getting a good view...
Enjoy
Fango