By default, Book Reviews completed by students are the only activities that display publicly on the Class Shelf. You can choose to also display your class's Practice Questions, in addition to Book Reviews, on the Class Shelf for all to see, including yourself as the teacher.
To display Practice Questions on the Class Shelf, click the drop-down arrow in the top right of your account and choose Settings. On that window, select Class Shelf on the left.
There will be an option to display both Book Reviews and Answers: