Tracking Modifications in Microsoft Word

I work at a college and occasionally we have students who turn in the same assignment for an online course. I know I can open the individual Microsoft Word documents and look under Properties to see if they have the same title or author, but that is not always helpful. Currently there are two students who have turned in identical papers. Is there a way to reveal text that was originally there, but was later erased? I think student X took student Y’s paper and erased her name and then put his name on the paper. Any help you could offer is greatly appreciated.