I work in a school and I am trying to allow teachers to access to change passwords of the students. I have applied the correct security settings on the OU in which all the students are stored to allow the 'teacher' group to change passwords. However, the security is only being placed on the OU and not on the user objects. I have looked at the security of the users and none of them have the 'allow inheritable permissions from parent to propagate to this object' ticked. There are about 1800 user accounts. Is there any way of changing all the boxes so they are ticked??

That seems to be the wrong way round to me don't you need a group that has the password reset option that contains all the teachers. If you apply to the users it allows the users to change the password. What you could do is delegate the control. highlight the OU then from the action menu select delegate control (this starts a wizard) select the users or group you want to delegate control to. When you select next you'll see common tasks listed one is reset passwords. After that you could make it easy for the trachers by giving them a taskpad (customised MMC) with the password rest as an action.

I have tried to delegate control but none of the user objects are inheriting. I have written a vbscript for the teachers to change passwords.

You should delegate to the teachers OU not the users