Please follow these steps to enable duplex printing on your classroom printer:
  1. Open the Settings app.
  2. Click on "Printers & Scanners".
  3. Click on the "Hewlett-Packard HP LaserJet Pro MFP M225dn".
  4. Click the Manage button.
  5. Click "Printer properties".
  6. Click the Device Settings tab.
  7. In the Installable Options section, toggle "Duplex Unit" to "Installed".
  8. Click the "Apply" button and close the printer and Settings windows.