You've nailed it!

-"Hey! teacher, you've really nailed it!"

-Today's lesson was all the same: students doing nothing but talking to each other, and not in English. So far, nothing strange, however, there was a question that I'd like to clarify. Not just because of the question itself, but simply because of someone's comment and composition. You know what: students wanted to catch me. Oops! I think I nailed it. So, the question is as follows: Can you write usually at the beginning of a sentence?

Yes, absolutely. Here's an example:

Usually we are melting snow or ice so we don't bother, but this trip could see us near stagnant water.


This example above was taken from the British National Corpus, which is like the Spanish Real Academia de la Lengua, but in the UK. You can also have a look at more examples like this one, clicking on here and here for further practice on Adverb order. So, do you still think that I was wrong in class? Of course, NOT. 
-"You've completely nailed it, teacher."