All that really matters is whether the PCN was issued because you were partly parked on the zig zag line, or for another reason.
What is the exact wording of the offence ?
Ask for a copy of the PA's attendance note, and photograph, if he took one.
If he didn't take a photo, which these days is unlikely, it will be easier for you to appeal successfully, because then it's your word against his about EXACTLY where your tyres were.
Indeed, if he did NOT take a photograph, you MAY wish to recreate the situation, and take your own, convenient photograph ;o).
Not that I'm suggesting that you lie to PATAS, or anything.
The fact that you work at any school is irrelevant to PATAS.
All that matters is whether you were parked on the zig zags, thereby almost certainly contravening the Highway Code.
On the other hand, the Council has a duty to ensure that its signposts and road markings are "clear, certain, reasonable, and fair."
If I were you, I'd appeal it in any event, because by doing so, you've got nothing to lose.
If you lose, you'll pay the £100 which you are currently obliged to pay in any event.
However, in my experience, when the council reads your letter, they will probably reduce the PCN by half, to £ 50.
It depends how far you want to take it.
If you take it to PATAS with the photo of the sign, and perhaps your photo of your tyres, PATAS may well cancel the PCN in any event.
As I say, you've got nothing to lose by taking it all the way to PATAS.
Indeed, amongst the PCNs which are appealed, roughly 50% of them get cancelled.
Talking of which, put this at the end of your letter :
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In the circumstances, I would suggest that your office cancels this PCN, or I shall be obliged to make representations to PATAS, which shall include
* a map and photographs *
of the confusing
* signpost and road markings *
, following which I shall be asking the Parking Adjudicator to condemn the council in relation to costs.
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When the council sees that you will be asking PATAS to condemn them in costs, they may well back down completely.
Let me know how you get on.
Best,
LoveableRogue
* amend as applicable *