Any image that can be displayed onscreen in a browser can be stolen or copied - all someone has to do is take a screen shot.
Your only real protection is to
1) watermark all of the images you upload with your name, website and copyright date
http://cameras.about.com/od/photoeditingtips/a/How-To-Watermark-Your-Photos.htm
2) only ever upload low resolution images (72dpi, under 600 pixels wide or high). This won't stop web use, but will limit the qualit for print use.
You can embed your info in the metadata of the image file, but that does no good if a copy is pasted into a new image file or if the data is stripped.
http://graphicssoft.about.com/od/exifsoftware/EXIF_IPTC_XMP_Software_Metadata_Readers_Editors_Extraction_Tools.htm
http://help.adobe.com/en_US/photoshop/cs/using/WSF23FB426-0A09-46de-91C8-BDB64CF378FA.html
Ask your college if they have a secure server site with password access only. That will limit the viewers to students with passwords on the system. Or set up your own website with the images in a password restricted directory, that way only the people you give the password to will have access.
There a couple of tricks you can do on a web page to make the image less convenient to simply right-click and save image as....
You can make HTML tables and place the images as Background images in the table cells, AMD use a transparent Gif as the foreground image.
You can incorporate a JavaScript that disables right clicking.
You can use a script to call the image from a calculated filename reference, so it is harder for the viewer to tell where the files are stored on the server if they View Source.
Etc.