Schoolgirl Desperation Panty Poop

Sitting at my desk I am (genuinely) desperate to poop but am denied permission to go, I ask a couple more times, before it’s too late and I unload it ALLLLL into my white full back panties. Shortly after we are dismissed and I go into the bathroom to check the mess, finding my white panties completely ruined with a huge load inside them, and a very messy ass.
Filmed solo.