This lesson is originally for my adult English conversation class - they are advanced students!
I think you could do this at high school with a bit of substitute Japanese explanation form your JTE. Could be a good icebreaker. But I don't personally teach high school!
It's a PPT explaining the British radio show called Desert Island Discs.
Everyone will take turns choosing a piece of music, a book and a luxury item they would bring if they were a castaway. It's a speaking presentation activity and listening too, you can ask comprehension questions after each person has spoken.
The target English is "If I were a castaway, I would bring...".
Second conditional, same as "If I were a cat, I would sleep all day.".
PDF so you can preview it.