Did you invite only a few parents to the Parent Teacher Conference that you set up to give them the first preference to sign up?  Do you want to invite the rest of the class now? Follow these steps - 

1. Click on the class name in the left navigation tray
2. Click on Signups in the Updates tab
3. Click on the Parent Teacher Conference event that you created in the Calendar feed
4. Click on Options in the top right corner
5. Click Invite More People in the menu
6. Select the <class name> to invite everyone in the class 
7. Click Done.
8. The message to the Parents screen is seen with the recipients in the To: field. 
9. Edit the message that is sent to the parents in the email.
10. Click Send.
11. Successfully Created message and the details of the conference are seen.
12. Email Invitation, Post in Home feed, invitation in the Calendar feed is sent only to the parents who have been invited this time.