You have full control over the notifications you get from the system. This includes control over how often you get notifications that your classmates have posted to discussions.
To set your notifications appropriately, click Account in the upper-left, then choose Notifications. In the resulting screen there are quite a few notifications listed, grouped by theme. The choices for each are:
The bell symbol: Notify me right away
The daily calendar symbol: Send daily summary
The weekly calendar symbol: Send weekly summary
The cancelled out bell symbol: Do not send me anything
Please turn off your "Discussions" notification, which otherwise will notify you each time a change is made to a Discussion on the administrative side. Below is a graphic of that setting in Notifications, and you can see that the setting is turned to off, or the cancelled out bell symbol. This said, please turn your settings for "Discussion Posts" to one of the settings that will allow you to receive notifications in your email or text (however you choose to set it up) if you wish. This will let you know when there are new posts in your Discussions.
Here you can see that Discussions is turned to the "off" position, and Discussion Posts are turned to "daily summary."