The interviewer wants to hear that you are passionate. As a teacher, you are a motivator. It is your responsibility to your students to provide a positive learning environment. If you feel mediocre about the topics you are teaching, that will be clear the interviewer. As you prepare for your interview, think about examples of when you have taught your favorite topic and why you enjoy teaching it.
"I enjoy teaching about citizenship because I am teaching about my favorite topics: human rights, equality, and freedom. My passion is apparent in my enthusiasm and in the way, I creatively present the topics. I like to facilitate discussions and role play. I want my students to know their rights and know their duty to their fellow citizens."