We used fountain pens to write with - I suspect that ballpoint pens were illegal; and this led to what might be described as Adventures with Ink: blotting and spattering.
Blotting is straightforward. The ink pens either had a reservoir of ink - with some kind of squeezing or plunger mechanism to load the ink from a bottle; or else they are cartridge pens when the ink was bought already inside a plastic tube - and inserting the cartridge would pierce the tube and allow the ink to reach the nib.
Either way, it was possible to compress the ink container and extrude a large blob of ink onto the work book of a best friend when their attention was diverted.
But this was rather dull - so the best effect was to make a deep blob - then covert it into a complex blot by pressing the pages together. If, then, the pages were slid back and forth, then the ink could be made to cover pretty much the whole of two sheets. If slimy spit was added to the mix, the lubrication led to even more damage.
Of course, this was a sort of 'nuclear option' only to be used in the case of extreme provocation or extreme boredom; and, analogously, liable to mutually assured destruction from retaliation.
One Biology lesson matters got completely out of hand. A group of four or six of us was sat around a table, doing some kind of practical work - look at plants down a shared microscope, or similar. It began when somebody like Jones blotted Tank's book - wit the full works: blob, blot and scrape. Tank deserved it for having his curly hair in a style which resembled headphones and for being generally a smug dandy.
But Tank could not get at Jones's book to retaliate; so the conflict escalated into spattering. Tank raked his fountain pen in a sweeping arc in front of Jones, whose head, neck and white shirt-front were diagonally machine-gunned with multiple blobs of ink.
Unfortunately, as so often in war, there was collateral damage - and some other got spattered by Tank's scything gesture; therefore the counter-attack was multiple and devastating. Jones plus others combined to empty their fountain pens, using short criss-cross sweeps, onto the cowering, muttering Tank.
I observed all this through a small crack in my school blazer - because I had seen the conflict brewing and retracted my head into the unfolded lapels of my dark navy blazer, upon which the ink storm spattered invisibly.
I was sufficiently impressed by the effect of the ink to hatch a wizard wheeze. I discovered that - if the ink was diluted sufficiently, it looked like ink, but did not stain. How I convinced myself of this is hard to imagine - but I believed I had discovered a recipe for create apparent ink havoc which after a few seconds would simply disappear like water.
And it seemed to work! I spattered various people and things, creating a sensation - but then before they could retaliate I showed them that it was a fake. Hilarity ensued.
Within about an hour the craze had spread, and a group of us found ourselves in the boy's toilets armed with pens charged with ultra-dilute ink and washbasins full of water for swift re-loading.
Chaos! Within ten seconds everybody was covered in the dilute ink, and so were the walls and ceiling of the bathroom.
At the time I insisted that the real problem was some stupid boys had failed to dilute their ink adequately - probably Roberts, because that would have been typical.
At any rate, when the Deputy Headmaster walked in (Why? - I never knew) there was a situation of apparent carnage. He was so angry that wouldn't listen to my protestations that things were not as bad as they appeared to be - and we all had lunchtime detention to clean the room and restore normality.
Whether it was because the ultra-dilute ink had dried in the meantime, or because of some flaw in my reasoning was never clear - but in the event, when we had to do it ourselves, it turned-out to be surprisingly difficult to remove the 'fake' ink spatters - it was almost as if they were real ink spatters.