As someone has said - the examiner may have a bit of a laugh and it may brighten their day a bit
However I doubt any of them would be impressed and a moody examiner may not be amused.
And realistically speaking tell people your local area is a bit of a graveyard for birds and the school headteacher stinks... well that defeats the point of your guide, which means it is ineffective and unpersuasive, in which case, even if the examiners have the right sort of humour to appreciate your jokes, they can't qualify your guide to give you many marks anyway, as it doesn't effectively answer your essay question.
I've put humour in my stuff too but I've put stuff like teachers marching like prison guards in the exam hall - as opposed to what you've put. Light-hearted humour is fine but I think you've gone a bit too far? Generally speaking what you've written would've been funny but considering it's an exam...
Well there's nothing you can do now anyway - just sit back and wait for results day. If needs be I'm sure you can resit or drop the subject!
and hey as a real reassurance, no sarcasm, in my modules I got AAD, with D in coursework - you would've thought I'd messed up, right? This is Eng Lit at AS. I came out with an overall A
I could've got AAE and still have got an overall A.
So you see, one module doesn't necessarily affect much