Do you work from some sort of syllabus? Or is it more free form? Also, what sort of age-range are your students?
We filter on intellectual curiosity and love of programming, so people don't typically have trouble finding interesting things to work on, especially since they're surrounded by other curious people working on interesting and hard problems.
I believe the youngest student was 19 and the oldest somewhere around 40. For the upcoming batch, most students are in their 20s or 30s (I don't know for sure, because we don't ask).