Oh yah, it's not a 50 minute activity. I've used it in addition to another activity, or in a period where we didn't have the full 50 minutes. You can include a short prediction activity before hand in order to prime students for predicting.making up stories, possibly with a photo, and have students predict what has happened or what will happen.
It does take some time for students to create their stories and share them with others, but the activity has never taken a full 50 minutes for me. I've got some particularly proficient students, so I'm assuming this would take more time with lower level students.
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Cheers.