It's the school rule. If you are going to give a valentine card, you have to give one to every child in the class. They have the same rule for party invites.
I really can't be bothered with valentines day and don't understand what it has to do with 6 year olds. So when dd asked if she could do cards, I showed her the class valentines list the teacher sent home and said, "you'll have to write one for each person".
She has decided not to bother
.