There are two options to whipping a Chromebook:

  1. Insert the SD card that is in the tech office into the card reader slot and follow the on-screen instructions.
  2. Wipe a Chromebook
    1. Press Esc + Samsung Chromebook Refresh key + Power. A yellow exclamation point (!) is displayed.
    2. Press Ctrl + D to begin dev mode, then Enter. A red exclamation point is displayed.
    3. Press Ctrl + D. The Chromebook deletes its local data, returning to its initial state. This takes approximately 15 minutes.If Forced re-enrollment is enabled for the device, you'll see a note that developer mode is blocked. This shortens the wipe process, and still allows for re-enrollment when the device automatically reboots into verified mode.
    4. When the transition completes, press the spacebar, then press Enter to return to verified mode.
    5. Enroll the Chromebook before signing in to it


Googles official channel:

https://support.google.com/chrome/a/answer/1360642?hl=en