To hide instead of uninstall those Apple Native Apps, such as Calendar, Voice Memo, Stocks, etc. you can:

1. In Admin Console, go to 
   1. Settings > School Policy > Apple Native Apps
      
      
   2. Switch on the App(s) you want to hide
      
      
   3. Tab Save 
      
      
2. Go to 
   1. Device Management 
      
      
   2. Bulk Action > Advance > Set School Policy