Be creative with group dynamics...
With 25 students per class it will not be possible for students to read and respond to everyone's posts so here are some ideas to manage or mix the activity...
*half of the students write original text post by WED other half respond with some flexibility: read 6 reply to 3
*of the students who post, half of the students post text, other half record audio
*student A posts an image - student B responds with text narrative - student A responds and/or posts another narrative.
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technical implications of original post = one author and comment being separated from original post