Leaving 'do' speech-jokes.

Tommorow night the headmaster at our school has organised a party for me because I'm leaving to work at another school (don't know whether that's good or bad!). Unfortunately that will entail making some kind of speech. Does anyone know of any jokes that may be good for a leaving 'do'? I teach music if that's any help. Anything would be appreciated.
I'm not too good on the old joke front so can't help there but a bit of a tip - keep it short and sweet. No-one likes a speech that waffles on (I'm a waffler and even i know that)!!

Best of luck with the new job.