I have always written a thank you letter to each child after a birthday party to thank them for the present. I wrote them myself when the DC were very young and they have been writing them themselves since the age of 6 or so.
My oldest dd is now 9 and I'm wondering whether it's still necessary. I've said a verbal thank you to the mums when I've seen them in the playground and dd has thanked a few people verbally.
Of course she'll write thank yous to relatives and people she doesn't see often but is it necessary to write thank yous to school friends? What do you do?