Which book has "Sorry So Sloppy / S.S.S."?

In third grade I read a book about a lil' girl who signed her letters S.S.S. (Sorry So Sloppy). If I remember correctly she was just learning how to write in cursive and didn't like her sloppy penmanship. What is the title of this book? I think it was written in the late 80's early 90's.