Can I grant permission to some of them, for them to be able to share with others?
Yes you can.
(You have already granted with rights)
In this case what they should do is:
Pick the files they want to share and right-click on them.
From the pop-up choose Share and in the new pop-up choose/type the emails they want to share with.
Depending on the rights ...
The setting to allow editors to share files applies to all editors. It's not possible to allow to do this to only few of them.
NOTE: Team Drives have more options but they apply at Team Drive level, not at folder level.
If your client has a Google Workspace (formerly G Suite) Business or higher account, ask them to create a Team Drive then move the files you uploaded there.
The above because if you upload the files to a folder that is in "My Drive", no matter if your client is the folder owner, the files consume your Google storage quota, and if you delete them ...
trying to organize all of my documents and slideshows into
folders...some of these documents and slides I cant move, the option
is just greyed out.
...these documents and slides have been submitted into classroom...
You cannot move your documents any more because you do not have editing rights any more. You just have viewing rights.
You will ...
You need to add a comment inside the PDF with Acrobe Reader.
Then upload it in drive, click on the three buttons on top of the comment and select "link to". Only in this case it works.
If you add a comment directly in Google Drive, it doesn't work.
Share the folder to the second account and use the chrome extension Copy Folder to make a separate copy with the ownership. This extension recursively copies all the files. To add to this, it also allows the copying of the permissions.
Now, in September 2020 this is still a problem.
I found two workarounds for this.
Open the PDF in OS X Preview.
Export the PDF and use the Reduce File Size Quartz filter.
The new PDF is fixed and transparency will not be printed in black anymore.
Convert the PDF into .jpg images using https://smallpdf.com/pdf-to-jpg and then print ...
There are many approaches to this resolving this question. The key is how to establish whether the first eleven characters of the file name signify a "renamed" file.
The rename format is "yyyy_MM_dd_". The date is separated from the file name by an "underscore". Had you used a different, perhaps unique, separator then you would ...