Calling all grammar curmudgeons

[SoupDragon]

I'm putting together a directory of businesses for the PTA. Where do I put the apostrophes? It's called:

Parents Services Directory

My mind is that there should be apostrophes after both final ss (which brings to mind another question - what is the plural of S?) but that looks too messy for the title!!

Ah now - an alternative would be Yorkshirelass' suggestion. Apostrophes are a blimmin' minefield!!!

snigger

As I said, I would not have given it a second thought before Mumsnet. Then I got worried that there would be a an apostrophe loving mumnetter in the school who would start a thread lamenting the gramma skills of the PTA.