how can I lock a directory with chflags schg ?

[Ensel Sharon]

I have a directory with particular permissions on it, etc., that I want to
make _absolutely sure_ never gets changed to different permissions.

So I figured, easy, I'll just:

chflags schg /dir

but I notice that once you chflags schg a directory, you can no longer
write to that directory.  Is this correct ?  Am I also correct that I
_can_ continue to write to subdirectories of the schg directory ? (I seem
to be able to)

Is there any way to lock down a directory the way i want to, and still be
able to write to it ?

Thanks.