No, when posts are deleted they're dropped from the database. Your only hope would be to restore a backup of the database. You could start changing the status of a post to depreceated instead of deleting it.

Thanks for the reply- I'll look into depreceating posts.

Reggie

i'm guessing that you would want to do this so you can monitor what the students have been posting?
If so, you will have alot of trouble as you would then need to replace the delete button with a deprecated button, and in the list of posts make it so students don't see deprecated posts anymore.
Also you might also need to research about comment actions.
And post and comment editing.

So to properly monitor posts with b2evo you will need to disable comment editing and deleting, and do what i said above with deprecating.

All of which is quite some work, except the comment editing/deleting that should be set by permissions.

If you are not monitoring the student posts, forget everything i just said ;)

Edit:
The simplist aproach would be to delete the edit/update button, and disable comment editing, and delete post permissions for the students.