I'm on the professor's side.

It would have taken the student all of ten seconds to hit "Save As" and select a more compatible file format. The professor should not have to jump through hoops or install new software just to open the student's files.

In this day and age, a student going for a Master's degree, as part of the college education process, should have had enough computer experience to be able to comprehend this simplest of tasks. (I'm aware that the world is full of people with degrees who are stupid, ignorant, and unskilled. But I believe this is a bad thing and needs to be changed as we move forward.)

Microsoft's idiotic insistence on creating new and incompatible file formats with each new version of their office suite is a completely different rant, of course. But at least give them credit for giving the option to easily save as other formats.