When my maths teacher was introducing us to functions, she wrote f(x) on the blackboard and informed us that it was pronounced "f of x". I shared a desk with a boy called Scott, who thought she was telling a letter of the alphabet to "f. off".

He spent the next hour repeating "f of x! f off x!" - experimenting with the delicious phonetic closeness of the two words - and giggling helplessly into his own neck. No-one else laughed at all. We were 14, and most of us were quite accustomed to telling people, things and abstract concepts to fuck off.
Flashers and Proud. An organisation set up by a group of 13 year old girls with the sole purpose of lifting up their skirts or tops at random victims. If anyone complains, they are presented with a FAP membership card and told to 'deal with it'.
Dubious entry, for a dubious practice. We would all go in the boys bathroom at primary school (girls may have practised this... though it seems unliikely). Whoever felt brave would sit on the floor with their back to the wall, hold their breath for 30 seconds, close their eyes, and cross their arms over their chest, while tucking their knees up to their chest. At this point 3 or 4 remaining boys would push his chest (with shoulders, arms) as hard as they could for a 10 seconds or so. Lack of blood (and oxygen) to the brain was the result. Unconsciousness of the individual ensued.

Variants involved using the stone wall in the playground, and an excess of 6 or more people pushing on ones chest. This nameless act was swiftly outlawed, in fear of widespread braindamage. It was none-the-less the best thing we 10 year olds ever did. Apologies if it has been posted under another name. Or if any of the kids from this Nottinghamshire primary school are permanently damaged...
An oft discussed playground myth was that there were men out there with penises so huge that, should they happen to get a full-on boner, they would actually faint due to the redistribution of blood from the other parts of their body. In hindsight this seems unlikely, although I would be interested to hear if it were medically possible. Maybe the purpose was to make the more conventionally endowed feel a bit better about their pathetic maggots.

Not that I have a pathetic maggot. In fact, I do faint because mine's so huge. Don't know why I asked. Case closed.
A girl who sat near me in 11th grade English came into class one day, looking rather sweaty and pale. As the teacher read from Tom Sawyer, this girl began to moan low like a wounded animal. Suddenly, her eyes rolled up into her head, she barked like a seal and then passed out, her face slapping down on the desk in front of her. But as soon her head hit the desk, she let off a fart like a goddamned foghorn. A fart which smelt like death.
Fainting was a brief but common practice amongst 7 year olds in 1979. The would-be fainter and his assistant would stand by the playground wall. The fainter would breathe deeply in and out as fast as he could, whipping up a nice dizzy spell of hyperventilation. After 20 deep breaths, he forces out his final emormous gob of air, and just as he does so the assistant lunged and pressed his chest against the wall as hard as he could. God knows how it works, but the fainter will immediately conk out and collapse, usually falling slightly unconscious and no doubt nearly dying in the process. I've no doubt Michael Hutchence did something similar on his final night alive, only he got his cock out first.
There was a brief craze in the final year of my primary school for mousetrap-type contraptions disguised as chewing gum. When you went to take a piece, a bit of metal snapped down hard on your unsuspecting finger. Hilarious!
At the age of eleven or twelve, my fingers were still quite wee (still are) and it REALLY BLOODY HURT. By the way.
One boring day in the grey and brown surroundings of my secondary education a fake hand appeared. We decided to try it out on one of the brothers (Jesuit in training) and placed it on his chair. He came into the room and did not sit down. He did not look in the direction of his desk or chair for 20 minutes. The tension was electric. When he eventually looked down and saw the hand/part of bloody arm (not particularly well rendered - standard joke-shop fayre) his face went a dead off-white and he squealed "Eeee! What have you little bastards done!" - we were all simultaneously stunned and delighted, expressing it in the only way we knew how... Whooping, hollering and laughing. When our mentor realised what was going on he turned a shade of red which, to my sincere regret, I have not seen anywhere since.
Consequence-free rudeness. Extending the ring finger, or making V-signs with the middle and ring fingers, will cause initial shock and offence, but when it is pointed out which fingers you are using, the parent or teacher will find themselves impotent in the face of your devilish wit. That's how it's supposed to work, at least.
Not a good idea in the presence of others, as they will all invariably start chanting "She fell over!" and push you over again, in a nearby patch of mud where possible. Falling over is an even worse thing to do in the lunch hall, where falling over can result in your lunch being tipped all over the floor and three hundred children laughing at you simultaneously. The headmaster will invariably choose this moment to walk in and randomly give a table of laughing boys detention as you run off crying. (You may recognise the voice of experience in this.)
Playground Australia Special!

A schoolroom version of the game show "Wheel of Fortune", also called "Duster Roulette".

On any hot summer day in Australia, the ceiling fans in each room will be running at the highest possible level. When the teacher leaves the room, a student in the front row dashes to the blackboard, picks up the board duster (which should be one of those big old wooden ones, not these modern foam versions which are, frankly, shit), screams "Fan of Fortune!" and then throws the duster into the fan.

A number of outcomes can occur:
1. The miracle of the duster passing through the fan untouched.
2. The fan smashes the duster in a sideways motion, sending chalk dust all over the room.
3. The fan hits the duster and propels it downwards on to someone's head. Hard.

Naturally, (3) is the best outcome. I still recall with fondness the moment when Patrick Dwyer - the fat-ginger-freckly-twat - got hit by the duster above the eye, splitting his eyebrow and spilling claret. Fantastic.
At the Bungay Town Fete, two kids dressed up as Klansmen and, I shit you absolutely not at all in the slightest, won second prize in the fancy dress contest. They lost to a kid dressed as a womble. The story amuses me so much because the fact that they came second almost suggests that the judges knew what a good Klan outfit looked like, and knew that Cobby and Jaff had missed some important gilding around the cuffs. Or something
The 'fanny banjo' (famously accompanying the willy orchestra) was abbreviated and concatenated to 'fanjo'. Playing 'Air Fanjo' was identical to playing air banjo, but with the strumming hand slightly lower than usual.
An incredible ability discovered by probably the best looking girl ever to grace our High School. She took to performing her talent during assembly, much to the surprise and delight of the remainder of upper school. After a while she appeared to have developed the capability of producing an inward 'sucking' noise to accompany the outward 'farting' noise, the only way I can describe this sublime sound is to have you imagine someone rhythmically thrusting a plunger in and out of a small bucket full of custard. She received such admiration for her expertise that before long several other girls had mysteriously discovered they shared her talent, producing sporadic low pitched squelching noises across the lecture theatre every other day. The final result culminated in daily renditions of the 'Fanny Farting Frog Chorus' that lasted for weeks, causing utter disruption and chaos. Fabulous.

I have since discovered many girls can perform this amazing bodily function, but for some inexplicable reason, don’t.
A liar. As is, "Psst! Wanna buy some fannies?". Unknown origin.
A girl - let's call her TS-B, made the error in secondary school of declaring to everyone that she had shagged Tom Cruise. We told her she was lying, but she wouldn't confess - so it was her own fault that her sexual appetite had a kind of open season declared on it. She started it.

"She put a hamster in her vag face first and it suffocated."

"She put stick insects up her fanny. They all died."
Inevitable first word after walking into any room in a Fonz-style way. Both hands were held out to the side, palms down, to hush the adoring crowds, and a gentle nodding gesture of recognition was made by the protagonist.
At aged 10, I got to first touch a girl's private parts under the table in school. It was very sexy. I was ten, and she pulled down her knickers to her knees under her dress during art class. I used the classic "dropping a pencil" scam, and went under the table.
I am now 32, and I should probably get a new fantasy.
(Uncle Log advises : why not re-enact the fantasy with a current partner or prostitute, then have sex? You might have an erotic version of that thing where you hear half a song and it's stuck in your head until you hear the whole thing. An important footnote to this advice is that the re-enactment should NOT be with a 10 year old girl. Unless she's got lovely tits.)
Example of a hereditary nickname, which curses all members of a family as they progress throughout the school. Began when Farmer Senior, a typical fuckwit, thrashed the rest of the class in the 'farming proficiency' test, getting something like 95%. Farmer Junior smoked vast amounts of gear and, to the best of anyone's knowledge, didn't know which way of a cow was up.
Farrow was a gangly kid who was assuredly mental, and ginger. One of those 'funny' ones.

Allegedly his parents had an obsession with lawnmowers, and had a vast collection. At Christmas a single lawnmower would be decked in fairy lights and placed on the roof of their house.

Towards the end of the year I was phoned by my mate Jon, who barked "You know Farrow? He's DEAD!" before he was inexplicably cut off. I thought it was a joke, obviously, but Farrow really was dead; he had hung himself. That should have been the end of it, but perhaps because of his eccentricity, comedy stylings became applied to his suicide. It became common knowledge, accepted fact that he had "Put the noose round his neck and stood on a chair as a joke, and then he called his friend and said 'come round and see what I've done!', but he accidentally slipped off the chair and really killed himself!" It seems pretty obvious to me that it was a cry for help. I mean, how good a joke would that have been? Friend Enters Room. Farrow: 'Hahahahhaha! Look: I'm standing on a chair, and I have a noose round my neck!'

Then it entered a new stage of ludicrousness. With that touchingly naïve manner that teachers possess, where they assume that kids will be traumatized by a pupil killing themselves - as opposed to, say, finding it funny - our tutor asked for silence so that we could discuss the matter.

"I just wanted to make sure everyone knew what happened, and had the right story." Then, unexpectedly: "Does anyone know the right story?"

Benham, of equally mental and ginger status to Farrow, put up his hand. With deadly sincerity (he was not complex enough to be this deadpan), he said "He was talking to his friend on the phone, when he fell over the balcony and hung himself on the telephone cord."

I looked around. There were no smirks, no raised eyebrows. "I see," said the tutor. "I wanted to make sure everyone was clear on this."

What!? I wanted to stand up and shout "For fuck's sake, he didn't accidentally hang himself with a telephone!" But I started to doubt myself. I still don't know to this day. Maybe he DID accidentally hang himself with the telephone cord. Or maybe people just couldn't accept that a ginger fool would die in a way that wouldn't involve slapstick.

Luckily, later that evening, my spiritualist uncle was on hand to give me some excellent advice: "You must pray to the Great Spirit for your friend-" "He's not my friend!" I never did pray to the Great Spirit, so if Farrow is in Spiritualist Hell I guess it's my fault.
An amusing way to spend a physics class. We all had to sit in the lab on stools that had small cushions on. These cushions were fastened to the stools with elastic, and they could be removed. In a moment of pure genius, one boy farted while sitting down, then got up, picked the cushion off the chair, walked behind the unpopular boy, and held the cushion to his face. This was the birth of the first fart transporting mechanism, and amused everyone for the remainder of the term.

And come on, who hasn't farted onto something and then smelt it out of curiosity?
In lieu of "Whoever smelt it..." debates, the chin defense could be used.
Once the scent of a bumtrump had been smelt then a clenched fist was attached to the chin. The last person to complete this action was identified as the fart culprit.
Of course, normally the first person to perform the chin defense tended to be the person who had farted - well aware of what they had just done and keen to escape the blame - and the loser tended to be anyone who had a bunged up nose or was too absorbed in colouring in the countries of Europe to follow the chinning trend.
This practice also evolved into double chinning, where the second hand should be placed below the first. Ultimately one would look rather like a Pharoah with one of those chin ornaments on - perhaps in his ancient regality a Pharoah was recognised as being incapable of letting off. I'm not sure, we did the Ancient Greeks instead of the Egyptians.
In my early school days we had a quite famous rhyme:
"Winnetou der Weise spricht:
Laute Forze stinken nicht,
aber die leisen,
die um das Arschloch kreisen,
vor ihnen hüte dich,
denn sie stinken fürchterlich"

For the non-german-speaking, here is a rough translation:
"Winnetou the wise says:
Loud farts don't stink,
but beware of the silent ones,
that circle around the arsehole,
for they smell terrible."

Winnetou was a native-american character from the popular cowboy and indian stories written by Karl May.
Back when I was at school - and right up to this very day - there is a rule of begging forgiveness for a flatulent outburst.

Trump - excuse me
Burp - pardon me

I still look at people askance if they get this wrong. Come on - its not fucking difficult.

[log]If you do find it difficult to remember, simply follow this rhyme. "Excuse me poos" (because farts and poos are the solid and gaseous states of faecal matter)and "Pardon your hard-on". For this second phrase, you need to imagine that you have just burped onto a man's erection. If you don't want to imagine burping onto a man's nice erection, try "pardon my lardon", and imagine that you have burped up a bit of bacon into a priest's beard. Actually, this one makes more sense. Forget about the dicks.[/log]
Setting Up : The two combatants would sit beside each other. Behind them would sit the Referee and his assistant.
Duration : A match lasted for a whole lesson. On good days, this can lead to some impressive scorelines and the opening of all windows. Scoring : One goal was awarded for each fart (farts had to be reasonably spaced - a quick follow up was regarded as a celebratory boot into the back of the net).
Fouls : Any 'fake' fart, whether intended or not, resulted in a penalty. A fake fart could be the players chair squeaking on the floor, usually followed by the player dramatically protesting his innocence to the ref, or a sinister 'professional foul' kind of fart, executed by the mouth. Or sometimes, while a striker was 'lining up for a shot' but having difficulty 'choosing his spot', he might unintentionally let out a groan or some other verbal effort. These would all result in a penalty.
Penalties : A penalty was taken by impersonating a fart. Easy, either by cupping the hand under the armpit, which resulted in a bit of a top corner net buster, or issuing a simple verbal 'prrrp' through a rattling, curled top lip, which was more of a simple tap-in, with the keeper going the wrong way.
Coaching : As the final approached unscrupulous 'agents' would try to sell their coaching services, which usually involved little more than them forcing you to get mushy peas with your bag of chips at lunchtime.
Rab Sutherland went on to win this in a tense and pungent final in geography, during which the teacher threatened to abandon the match at several points.