In the slang of the elite privately-run schools for the privileged = In the language used by the small and unfairly well-resourced schools run outside the state education system.
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What the writer says about dropping unstressed syllables to get 'soccer' is wrong. The derivation is right, but the mechanism is wrong. The main stress in 'Association' is on the /eı/; this syllable is dropped as well as the unstressed ones, and the one with secondary stress - /səʊ/ - has the vowel modified to /ɔ/. Also, the unstressed /si:/ becomes /k/.