Luke1307

Hi there, I read a book years ago but can not remember the title or the author, if anyone can help that would be great. It's about two young kids, a boy and a girl who write letters to each other's while arguing such as "your not invited to my party" etc. But they grow up and move away but still write to each other. It was a funny and lovely book and want to re read it but can't think what it is called. If anyone can help that would be great. Thank you.