Students can't delete the TD subject folders because they are not the owners of those folders. However, they can remove them from their view in "My Drive" so it appears that they have been deleted. If students remove or rename the TD subject folders from their "My Drive" either the student or the class teacher can often fix this.
Firstly, ask the student to check in their "Shared with me" in their Google Drive (or "Incoming" in the new Drive interface). If the folders are there (usually the case), simply drag the folders back to "My Drive".
If the folders don't appear in "Shared with me" then the class teacher can use Teacher Dashboard to solve the problem. In Teacher Dashboard:
1. Open the class
2. Click the Class Info tab and scroll to the bottom of the page.
3. Click the "Fix class folders" link.
Note that it can take up to 30 minutes to restore the folders.
Please note: TD can only restore the TD folders and the files stored in those folders. If the student has deleted their own folders or files, they will be in the bin and can be restored from there. If the student has emptied the bin then you'll need to contact ICT Service Desk to have them restored (must be within 30 days of deletion).