This is a lesson I have done with my winter camp high schoolers but I intend to do it with much lower level students later this week. I got the idea from a teaching presentation I saw by a couple of Korean teachers who studied in the States for 2 months.
Basically, the students are presented with the ambiguous script. They read it and you brainstorm the possible emotions of the people speaking in the script (keep it simple if you like happy/sad). Then once you get the emotions done (and it can be anything really, try reading enthusiastically yourself) you then brainstorm situations that the script might apply to (break-up, birthday etc). Next, you divide the kids into pairs, have them decide how they want to read the script and then have them perform in front of the class. The class must guess from the kids' acting skills what the emotions and situation are. I had one group whose situation was pressing the red button to start a nuclear war. Admittedly they were super smart/creative kids.
This works best if you have them do whatever warm-up activities you usually do when having them do drama. I like "seeker/avoider" and "blah blah blah" as the kids don't have to use English so all levels can warm-up with these two. Just demo them with the best student in the class.
If anyone has an ideas or could change the script to make it more ambiguous, I would welcome them. Thanks.