The Kissing Hand, by Audrey Penn, is a great antidote to back to school anxiety. Chester racoon is nervous about going back to school. So Mama Racoon teaches him a trick--the kissing hand--to ease his jitters.
I think this book is great for kids of all ages and any time mamas and their offspring have to be separated. My son loved the story (even though he is not nervous about school) and wants me to read it over and over. You can find it HERE.