If I ever went a decible or two too loud in public my mother would squeeze my hand and whisper, 'you will be in trouble when you get home'

Rarely heard a screech or a scream from me!

Mum said no...she meant it

If an adult cant control a 5year old then its lack of effective parenting skills

you dont convince a child you just tell them.
and kids dont have a higher IQ
its another excuse for poor parenting