Not so much slang, but our six year old had a spelling test at school last week. I'll try to use appropriate phonetic spellings so you get what happened. The teacher asked the class to spell a word that sounded like 'PIER' to English ears.
When they marked them, my six year old had got that wrong, but he was adament the word was spelled 'p i e r' so he went up to the teacher. "Oh no" she said, "I meant a 'pier of shoes" .
