I taught DS and DD our home phone number from an early age - certainly by 6 they knew what it was, in the form of a merry little jingle.
Three times this term DS has had friends over to play, and they then wanted to stay for tea / go to the skatepark etc.
I asked them to phone their Mum/Dad (on our home phone) to check- none of them knew either their home phone number or either of their parents' numbers.
"I've left my mobile at home" was the best response.
AIBU to think that, irrespective of modern gadgetry, knowing your home phone number, aged 11, should be normal practice?