This has worked in the two schools i have gone too in australia.
Step 1: Make Sure Your Laptop or Pc Has a New Account to Log Into
Warning: this inscrutable will only work on laptops with a wifi button or switch....
You will need a school account that has never logged on to the device before and type it into the login screen.
When you press wait about 1 second then press the wifi switch on i laptop or unplug the ethernet cable for pc's.
This will prevent the account to receive any restrictions and allow full access.
Step 2: Change Local Admins Password
Now go to user accounts and press "Manage user accounts"
you will receive a list of the accounts on the pop up an you can from there press on the local admin account and press reset password at the bottom
Step 3: Do What Ever You Want!
Thank you i hoped this helped.... Comment if it did!
WARNING: I am not responsible for anything that you do with this instructable