Haiku gives you the option, "Don't send notifications about updates to page content" when you first create a new class.

This setting will determine whether updates to Pages and Content Blocks are sent to students, parents, and co-teachers in your Roster. Checking this option overrides user preferences to receive daily page content notifications from this class, and these updates will not be sent. This setting can be changed at any time through the Manage Class > Class Settings area.

When should I send or not send update?

As a Teacher, this is completely up to you!

• If you have a resource or Extra (non-curricular) class where as a teacher you feel that page notifications are excessive, you can check this setting to prevent your students from automatically receiving these emails.
  
• If you want students to be notified every time you update a page, you should uncheck the setting so that they can get these notifications. Of course, you can't force a student to receive these notifications, but you can allow for the the option. (Any user can turn these notifications off through by adjusting their Username>Notifications settings and unchecking all of the boxes.) 
  

User Settings

To access your Notification Settings, select "Notifications" from your "Username" drop-down menu. Adjust individual notification settings for Announcements, Comments, etc. by clicking on the check boxes next to each notification type. To unsubscribe from updates to Page and Content Block changes and additions in your class, uncheck the "Daily Email" settings next to this option. Be sure to click "Save" when you are finished, and you should be all set!