Say students were doing their music subject, they can use scratch to create their own song. This is a fun creative way to generate rhythm with the incorporation of visual programming skills. I would give students a tutorial of how to navigate scratch before hand and then split them into groups to help each other create a cool song.
Another idea for a classroom activity involving scratch may be to create a story, for a literacy subject. This task would be an individualised task involving students firstly planning and executing their storyline before using the application.