This book was probably published in the 70’s. Story of teens in a mental (?) hospital working with a new (?) young doctor trying to connect with them. One character is named Bonnie and she is mute or doesn’t interact with people but likes when the doctor (?) sings “My Bonnie Lies Over the Ocean” so he starts to change the words and sings things like, “My Bonnie Lies Over the Pizza”, etc. Character called Zero was, I think, male, and I think, dies at the end. It was a small paperback size book with a hardcover that I read in the 80’s from my public library. I believe the cover was white.