Teachers may not want students to see what activities are coming in the future. It rests from the freedom or deleting or adding activities. I don't seem to find a change this.
You can find more about safe mode here:
https://help.extemporeapp.com/en/articles/4554621-enable-safe-mode
You can find more about safe mode here:
https://help.extemporeapp.com/en/articles/4554621-enable-safe-mode