Literal Answer

As Julie steeled herself to "show them" who she was "under that uniform", as her teacher put it, she took a deep breath that had the unintended effect of doing just that!

rrrrriiiiiIIIIPPPP!

As her chest expanded to breathe in, the pressure was too much for the Velcro on her top, and it suddenly burst open, the garment falling to the floor, baring her modest chest and tiny, hard nipples to the entire class! Julie reacted by crouching down to retrieve her top, but left her hands on the table for stability, pinning her skirt.

rrriiiippp!

A short, barely audible sound of the Velcro holding her skirt closed being released excited in Julie's ears. Acting on reflex, she stood bolt upright, leaving her clothes on the floor, and tried to cover as much of her body s possible with her hands. Of course, since she couldn't see very well, she had to judge by touch. Her hands groped her chest until she found her nipples. She cupped one in her hand as she moved her other hand to cover it, making sure her arm brushed against her bare nipple to keep it covered. Once her chest was covered, her free hand slipped down her body until she found her pussy, and cupped it. To her, she felt like she was cleverly covering up. However, to the students AND the teacher, it looked like she was fondling herself, and was about to do something even more intimate.

"Okay, you shown us enough, Julie. Take your clothes back to your seat before I call the principal! Those kinds of shenanigans were probably what got you kicked out of your last school, so I'll overtook it THIS TIME. Anyways, onto the day's lesson..." Ms. Shinagawa said as Julie collected her uniform and find her seat.

Julie was blushing deep red. She had no idea how it happened, but she had to deal with it now. The only problem was that she didn't see, and she had no clue how to put the uniform back on. She consulted her friends, who helped her put her clothes on, making sure the top was a little looser so she won't have a repeat performance for a while.

The rest of the class went fine, despite what happened. Afterward, they went to their next class.