Parental control problems

I have set up my iMac with Parental controls for my daughters, to 1 hour a day use and time limits of between 2000 and 0600.
However, although a 15 min warning until logout shows up on screen, the Mac doesn't automatically logoff after 1 hour as stipulated and continues to allow use, until the user feels ready to exit of their own accord.

1. I have used Repair permissions to no avail
2. I have even archived and installed to start afresh
3. All updates are installed as they should be
4. Repaired permissions again after updates as well

This is the sort of thing that Permissions repair comes up with and even though the repair is announced as complete, the problem persists:

Permissions differ on "Library/Application Support/Apple/ParentalControls/ALRHelperJobs", should be drwxrwxr-x , they are drwxr-xr-x .

Is their a way of getting deeper into the system to manually change this stuff?
Thanks in advance