There might be a question that you wish the admissions officers had asked, but you don't see anything about that in the prompts. Unfortunately, there's not really any way around this situation. You have to respond to the prompt that you were given. However, don't give up hope. Many schools will give you the opportunity to write a brief essay about anything you feel that the admissions officers need to know.
I still hadn't written anything about homeschooling. So, I sat down at my computer and wrote two pages one night about homeschooling. I based my essay on workshops I'd given, on my National Merit essay, and on questions that people asked me all the time. I wound up doing very little editing for the final version. I found places to fit this essay in- Princeton had an optional "anything else you'd like to tell us" form and Sarah Lawrence had a required essay about anything that wasn't covered elsewhere in the application, but for most of them I just sent it as an extra, with the cover letter reading "enclosed please find Form 2, my theater resume, and an essay describing my home education." Sarah Lawrence also required a graded academic paper- the most recent thing I'd written that was graded by a teacher was a theater review, so I sent that in. Officially, my part was done. So I thought.
Tips on How to Write College Essays about Anything