Powerwashing (formatting) a Chromebook
You'll have to switch to Developer Mode in order to power wash a managed Chromebook.
All of your personal data saved on the device will be deleted. Make sure you've already backed up your stuff. Data stored in the cloud will not be deleted.
Switch to developer mode
With the device fully powered off press ESC+REFRESH+POWER keys at the same time for 5 seconds and release. The machine will power back on.
You should a warning telling you that Chrome OS is missing or damaged.
Enter developer mode
Press CTRL+D and then press Enter. Chrome OS will reboot into Developer Mode and you will get another warning.
Reset your Chromebook
Press SPACEBAR and then press ENTER. You will see a message saying that OS Verification is turned on. Your Chromebook will automatically reboot.