This question has been given to my year 7 son and he has permission from his teacher to seek help from the web! Any assistance gratefully received.
"A wicked year 7 pupil, the self-styled "Logician", was up before the year head on a serious charge of misleading the rest of the year into avoiding homework through clever argument. The head of year promised expulsion from the school, but added the following strange condition that, if on the day of expulsion the Logician signed a statement making one true declaration about his punishment, the expulsion would be reduced to confinement in the Head's study for 10 days. If on the other hand the statement is false, then the sentence will be carried out immediately. The day of expulsion arrives and the Logician, beaming, signs a declaration which is handed to the head of year who reads it in bewilderment. Tearing the document to shreds in his anger he orders that the Logician suffers no punishment whatsoever."
What could the Logician have said which resulted in receiving no punishment at all?