Security Access For Sharing

I was unable to set the security for different people privileges at
subfolders under a parent folder. The scenario is like that one parent folder
and inside have a lot of subfolders. But this subfolders I only give to those
users to have access right to that particular folder only and the rest should
be in read mode only. I was unable to set it eventhough I already disable the
inherit inside the advanced of parent folder but it still control by the main
folder. Eventhough I try to control from subfolder all the security is still
given to the parent folders.