Deleting work as a teacher on my own account

Hi, i’m new to I am a teacher. I’ve worked my way through the lesson activities to get to grips with them. However, now I now want to wipe clean all the examples I’ve made so that it’s all cleared ready to model to the class. At present, when I revisit any lessons, all of the tasks are green and completed so the answers are all visible on the board. I hope this makes sense. Any help would be appreciated.