The "Created" date is the date the file was originally created and
first saved. If you're using a template file that was distributed (by
the instructor himself?) to the class then everyone using that file
will have the same "Created" date. Does anyone else that same Created
datestamp?

The "Modified" and "Last Accessed" dates, also on the statistics tab,
should be more or less unique to all students. I say "more or less"
because it would not be too far a stretch to see everyone completing
their work the night before it is due, but the timestamp portion is
more likely unique.