I remember when I was growing up, a child in my primary school class lost her mum...next mother's day, we all made mother's day cards at school and she was told to make a card for her dad 
I lost my mum when I was in secondary school...I hated mothers day.
So many children may have lost parents, have absent parents and all sorts of different situations which make these days hard for them.
Aibu in thinking schools should just ignore these days and not get the children to make cards?