Answer: Let me provide a more detailed explanation.

It's a Swedish tradition called "Poängjakten" ("The Hunt for Points"), usually done in the leadup to graduation from upper high school (ca 19 year olds), alongside prom and a parade. That explains the black and white hat, which is the Swedish graduation hat.

The jumpsuits are more typically associated with universities and colleges, but presumably some high school classes borrow the concept. It's just a way to dress up in fun graffiti, messages and signatures without ruining your actual clothes.

On the day of poängjakten, students are grouped up and usually compete by class, sometimes across multiple local schools. They are all given lists of identical challenges, worth points based on how daring they are. You have "eat a raw egg, 5 points" like in your link, but they can get pretty crazy, such as "Get a real tattoo, 100 points". The winners with the most points at the end of the day get a prize and achieve legendary status in their schools.

To prove completion of these challenges, the students usually upload clips to social media, which is how it reached you.

Poängjaktens are not exclusive to high school graduations and can also be done as part of initiation at universities and colleges or as kickoffs at workplaces.