Bastard Week
An impromptu celebration, where colleagues took part in such activities as 'knee kicking', 'gobbing in hoods', and 'throwing people down the stairs'. I stabbed my mate Andy with a compass in maths.
He got sent out the class for screaming in agony, but still asked me to be his best man in later life. Although he was soon divorced, mind.
written by Di*in* B*stard, approved by Log

also consider :
random and impromptu slashing of the neck with metal combs, and surprise karate chops to the Adam's apple 10 seconds before a teacher enters the class.
This results in a complete inability to breathe, so you won't be able to answer the register. Which will obviously be your number one concern, what with not being able to breathe.
written by da*e e*an*, approved by Log

In Chemistry one day, Sam remembered we had a French exam next lesson. Nothing serious, just a round-up of a chapter in Tricolore.
However, Sam hadn't prepared for it, so asked me to smash him over the hand with the base of a retort stand. I obliged, and hey presto - one French exam avoided! Not to mention the kudos of having two broken fingers and spending days in hospital.
For a later chapter in the book, he actually stabbed himself in the hand with a Stanley knife.
written by Da*e Har*is, approved by Log

Having both forgotten our swimming kits, a friend and I searched around for something - anything - that could help us avoid the inevitable splashing about in pissy water wearing some gippos' swimming cozzies from lost property.

We ransacked our bags for something to help us get out of PE. Unfortunately, the best we could do was a lowly packet of Strepsils. Clinging to the forelorn hope that the packet's warning against eating too many Strepsils in a 24 hour period would cause illness or some kind of allergic reaction, we devoured the entire packet of the potentially lethal lozenges beween us.

Not a lot happened. We didn't choke on our swollen tracheas, or experience even the slightest form of anaphylactic shock. And so it was that we found ourselves swimming in pissy water wearing gippos' swimming cozzies from lost property. The inevitable tabloid headline "School's Shocking Strepils Suicides" would have been less embarrassing.
written by He* Phi*lip*, approved by Phil