Do you want to Invite your parents only using emails? Disable class access code you have generated by following these steps - 

• Click the All Groups at the top left corner.
• The left navigation tray opens up.
• Click the name of your class under the Classes label.
• Click the Access Codes Icon (key icon)
• Click For Parents or For Students
• Turn off the Enable Class Access Code toggle button in the Parent Acess Code Screen
• Class Access Code is turned off for your class

Note: The class access code which was generated for your class will no longer be valid. You have to invite parents using their emails. 

Also view: 
Generating Class Access Code for my class