When students are changing for sports in a hurry and accidentally put on someone else's underwear from the pile. This has happened in some schools. A girl put on the wrong underwear and realized it when she felt really uncomfortable. It was a very awkward situation to be in, especially when she had to try to find the right owner to swap back.
One common one is when the elastic on the underwear breaks during the school day. This can make it uncomfortable and also cause some embarrassing adjusting. For example, a girl was sitting in class and suddenly felt her underwear slipping because of a broken elastic. She had to be very discreet about fixing it.
Forgetting your lines during a play rehearsal or performance is quite common. You stand there looking stupid while everyone else is waiting for you to say something.
One common one is when students have to get vaccinations at school. Some students are really afraid of needles. There was this one boy who started crying and screaming before the injection even started. His classmates all watched and it was super embarrassing for him.
Probably the most common are those related to wardrobe malfunctions during school performances. Imagine a dancer on stage and their costume suddenly becomes loose or reveals more than it should. This not only embarrasses the student but also can be quite a shock for the audience. Also, there are times when students forget to bring proper clothes for a particular activity, like not having a swimsuit for a swimming lesson and having to deal with that awkward situation in front of classmates.
One common one is getting called on in class when you don't know the answer. You just sit there, stuttering and trying to come up with something, while the whole class watches. Another is having your pants split or something similar happen during physical education. It's so embarrassing to have everyone see that.
Tripping and falling in the hallway, especially when you're trying to look cool in front of your crush. You might be running to catch up with friends or just walking casually, and then bam! You're on the floor and everyone around is either laughing or looking at you with pity.
One common one is when students forget their lines during a school play. For example, my friend was supposed to say 'I'll be there for you' but instead said 'I'll eat you for lunch'. The audience couldn't stop laughing. It was really embarrassing for him but super funny.
Once, a girl's skirt got caught on a bench and her colorful underwear was exposed. She was so embarrassed that she ran to the bathroom immediately.
A very common embarrassing story for high school freshmen is during sports tryouts. They might overestimate their abilities. For instance, a freshman who thinks they are great at basketball tries out for the team but can't even make a simple layup in front of everyone. Or during a track and field tryout, they trip and fall during a short sprint. It's not only embarrassing but also can be quite discouraging for them at that time.
One common element is public humiliation. Like tripping in front of a lot of people or messing up in a public performance. Another is related to crushes. Doing something silly in front of the person you like can be really embarrassing.
Forgetting your school supplies is a common one. You sit down at your desk, the teacher asks for something, and you realize you left it at home. It makes you feel unprepared.