I've never heard of Microsoft checking up on student/teacher editions to make sure the buyer is legit. In this instance they put you on the honor system--probably because as long as you're using their file formats they're happy.
But who cares if you can't upgrade the student version? Whose ever needed an upgrade to MS Office? It's the same stuff for the last 10 years. It should be like the Doc Martens I bought 13 years ago-I haven't worn them out yet so I still wear them.