Advice on an upcoming research project

Hi! I am a new member, and I am looking for some advice on an upcoming project I have to do in my teacher education program. It is called a "Teacher Research Project." My job is to develop a research project where I develop a lesson or mini-unit about a particular topic and test students before and after to determine their progress. This is to be implemented during my student teaching internship in the fall. My teacher suggested doing something quick and easy that will still be of some benefit to the students, like common grammar errors or something. However, I'm really interested in doing something with creative writing, because I am a writer myself. I'm looking for advice on how to develop a mini-unit for creative writing that I can easily measure through pre- and post-tests. Do any of you have any ideas?

Thanks!