users locked out

My school win2000 network serves 1300 pupils who frequently lock themselves out. At the moment I have to go into each user’s properties in ‘Active Directory Users and Computers’, and remove the tick from the ‘Account is locked out’ box.

Does anyone know how to bulk remove this tick from all user objects in an OU container? I’m guessing that some scripting is required but I don’t have much experience in that! Can anyone help?