Convey the plot in 30 minutes!
You must confidently know the plot of whatever you are trying to introduce, as the storytelling relies entirely on your skillful and clear narration.
If at all possible, put different families or groups of characters on different coloured card to make it easier for everyone to remember who is on what side.
For example, all Capulets on green A4, all Montagues on red A4 and all non-family characters on yellow.
For example, pull out all the three witches and narrate the opening in brief: "three witches meet on a heath (gesture for the relevant students to join you, each holding his/her name card in front for all the class to see) and they plot something spooky involving Macbeth!"
Make it as dramatic as you wish, adding as much atmosphere as you wish with your own acting skills!
At the end of every scene you waft your big stick or magic wand or whatever you are using to signify the change. Tradition has it that it is at this point you say, "whoosh whoosh whoosh whoosh whoosh!" as you spin around wafting your stick dramatically!
At the end of scene changes all characters return to their seats.
Perhaps this will be them simply writing the plot, making a card sort which they will have to do next lesson as a recap?