When the Files/any details posted in the announcements are not visible for the parents,then kindly check the approval settings of the announcements.Follow the path given:
Settings-->Organisation-->Organisation settings-->communication Settings-->Announcements
If approval setting is enabled,then the details posted in announcements should be approved by the principal
then the details will be visible to the parents. If approval setting is not enabled,the announcements' details will
be directly posted in the parent portal.