Yes, sorry but your are being unreasonable. You don't say how old you GC is but having GC of various ages attending schools at different levels I'm only too aware of how some parents and grandparents dress!
Obviously, GC school does not want people turning up to this event in leggings, crop tops, jogging bottoms that reveal "that awful builders bum", low cut tops worn over "rack-em stack-em" bras, any type of soiled workwear, mini skirts that leave nothing to the imagination, onesies................the list goes on.
I wouldn't expect time off work - pet bereavement
Mother staring back at me - realise you're getting older
Names I've not heard - don't know 90% of celebs