The way porn mags circulated at school was interesting. At the age of 12, the only way to see a porn mag was if a friend sold it to you. The same battered copy of Escort would be sold to one person for £1, then a week later sold to someone else, occasionally for a profit, and occasionally with the reader's favourite picture removed. And so on; until the same old Escort had half its pages missing, all its remaining pages stuck together, and sold for about £8.50.

This also presented a keen opportunity for the playground entrepreneur.
Copy of low quality jazz mag - £2ish
Pages in low quality jazz mag - 50ish
Individual resale value of page - 20p
Near instant profit - £8
In a particularly ingenious twist, I sold the pages by a sort of raffle mechanism whereby the purchaser would 'pick a number'. Thus, pages without pornography were simply "unlucky" rather than "unsellable".
Obviously, there were certain overheads to be accounted for - the cut you'd have to give your elder brother to buy the magazine in the first place. However, these were easily outweighed by the cachet gained from being the school's answer to Hugh Hefner.