Teachers can join classes and participate in zApps and zApp Books too.
To join a class, select the class administrator from the Select Teacher drop down. Then select the class that you have been asked to join. You will be asked if the details you have selected are correct. If they are not, select No and re-select the correct fields. If the details are correct select Yes and you will automatically be added to the class list and will start receiving zApps and zApp Books assigned by the organizing teacher.