Musicals are always a popular choice. Take a classic story and add contemporary songs to it to bring the story up-to-date. Choose a fairy story that everyone already knows to make the storytelling simpler. Imagine Cinderella singing the Pussycat dolls "Don't Cha" to the prince and you get the idea. Incorporate costumes from a particular era to add drama and a new setting, such as Mary Quant mod-inspired sixties or Dallas-style eighties glamor.
Rework a Shakespeare classic. Romeo and Juliet has been remade many times. Think of the differences between West Side Story and Grease, then look at the similarities. The Taming of the Shrew has been remade as Ten things I Hate About You, but the plot line is instantly recognizable. Choose a story that captures students' interest and rework a new setting. The Merchant of Venice could move to New York have a Wall Street setting.
Everyone loves to dress up so choose a pirate swashbuckling adventure, taking a few tips from Johnny Depp's character, Captain Jack Sparrow, for inspiration. Write a new adventure or read Treasure Island and recreate the dangerous tales of the high seas on stage with thunder and lightning and a sword fight or two.
A good "whodunnit" is always a popular choice. Settings can be simple or elaborate and costumes can fit in with historical periods or be modern-day. Choose a classic story, such as an Agatha Christie mystery, for an intriguing plot line, but don't let anyone find out until the end who is the guilty party.