I am using Xiaomi (MIUI 9)

Step 1: Tap on the "Settings" 

Step 2: Goto "Notifications & status bar" menu

Step 3: Now tap on "App notifications" 

Step 4: Now find "Skooly" app, on the list of apps and tap on it

Step 5: Now at the top, there will be "Show notifications", slide the toggle to enable notifications

Now you will receive notifications from "Skooly" app