I read it in the early eighties but it would have been published quite a bit before that. It was a girls boarding school and I think there were a few books with the same characters in , if not a series. There were 2 sisters. I can't definitely remember their names but I think the youngest may have been called Felicity. She had a copy of The House At Pooh corner and used to quote from it on occasions. Can't remember more than that but have been trying to remember it's name for over 10 years! Really hope someone else remembers it!