Notes in Class (Scribble Witch #1) by Inky Willis

When Molly’s best friend announces that she’s moving to a new school, a blue Wednesday becomes the Worst Wednesday Ever.
That is until some unexpected magic brightens up Molly’s day. Notes, a secret paper witch, springs to life from her pen pot – and into action! Some of the things Notes does are absolutely NOT helpful and gets Molly into trouble with her stinky teacher. But it’s surprising what one tiny witch, armed with nothing more than a pencil, can achieve before the home-time bell rings..