How to Erase Everything on an iPad When Locked Out
You can erase your iPad by restoring the device using iTunes on your computer. The restoration process will wipe all data from the iPad, including apps, music, videos, contacts, calendars and any personalized settings such as security PINs or passwords. The restore process is often necessary if you were given an iPad by a friend or family member or if you purchased a used iPad that is still locked. After the wipe is complete, you can set up the iPad with your personal information and reconfigure the security settings as you see fit.
Connect your iPad to your computer using the standard iPad USB cable and launch iTunes if it does not open automatically.
Click the iPad icon and then click the "Restore iPad" button.
Click "Don't Backup" and then click "Restore." The iOS software will be reinstalled on the iPad, after which you will be able to set up the iPad as if it were a brand new device.