Here is an essay I made for Lesson 16. It's a story that consists of verbs that are not written in the past tense, which is the emphasis of this chapter; there are also a couple of mistakes that do not involve verbs, but the trick is to get the students thinking about grammar. I recommend that Native Teacher read the story out loud, as the students listen and find mistakes, and have the Korean Teacher write the corrections up on the board with the mistaken words crossed off and proper verb/words right next to it. This actually worked well with all my classes, including the tough ones.
I've also included the Key....Enjoy