Sandra from Sugar Cubes and Spice Cake shares a tutorial at Sew, Mama, Sew! for making a desk bag to hang on the back of a school chair. Children in younger grades often sit at group tables rather than at individual desks. These seat sacks keep their notebooks, pencils, crayons, etc. with them during the day. Her version of the desk bag has two pockets, and is trimmed with ric rac and pom poms. Get the tutorial.
[photo from Sugar Cubes and Spice Cake on Sew, Mama, Sew!]