There is a drop-down list (above) with writing ideas/prompts. If you don’t know what to write about, or how to start, check this list.
Even if you do know, check this list.
Meantime, I wanna say something about “teaching” writing, if I may. I think that people have the questions all wrong.
The question isn’t so much “How can I be a good writer?” or “How can I write better?”
The question you need to ask, is “How can I use writing as a tool and a method for encounter; how can I use it to enter into conversation with my experiences?”