If for some reason the school needs to cancel an event, this is a two-step process:

Step 1: Send the parents an email (to inform them of the cancellation)

• Filter to the event under show more in All Prospectives
• Select all the users
• Bulk Action > Email
• Choose Cancelled Event template 
• Preview and send

Step 2: Set all users as cancelled to disable any pre-event automated emails

• Go to Events list and Edit the upcoming event in question
• Scroll down to the attendees and select all 
• Bulk Actions > Mark as cancelled