There may a situation where a student post has content that you don't want parents to see, but you don't want to delete it either.
Examples could be:
The easiest way is to just click on the folder icon at the bottom of the post, and select Private Folder from the top. You'll get a reassuring confirmation message that that post is not only visible to teachers of that class (and anyone looking at your screen).
Should you decide later that you want to make the post visible to parents and the child again, just deselect the folder.
*This would need to be an exceptional circumstance, generally a LJ should be a space where sharing a child's struggles with learning can and should be a common inclusion, albeit with a folder label, caption, or comment that reassures parents that you are aware of this misconception, and will be working in it, this is what formative assessment really looks like.