Hi David,
Thanks for your comment. I fully agree with you. The school I went to did actually encourage independent thought, although academic study totally bored me.
But when (at the age of 39), I was faced with this exact same question for the project module of an electronic engineering course at technical college, it took me only a few seconds to review my general knowledge of various subjects that I knew something about, and could research more deeply, to decide to tackle "The History of Computers", (Though I subsequently whittled it down to "Understanding the PC.")
Everyone else in the class (a good mix from teenage to forties) came up with an idea within a few minutes. It would never occurr to me to ask anyone for ideas, so thus I ask these students "What interests you ?" etc. (I would expect the course tutor to put such ideas to the students anyway.)
Teaching on how to think, how to learn, how to research, how to plan, etc., and both logical and lateral thinking, would benefit most people.