This seems like a neat tool to use with students. If you were to use this tool with them, would you provide some training on how to use it? This could be interesting to use with feedback. For instance, if you see that a student is misusing a word or phrase, you could direct them to Google N-Gram and have them search for it. It might even be possible to give them the correct use of the word or phrase and have them search for both. They could see which one is more common and decide which one is correct given the context.
Are there other corpus sites that you like to use?