Once you feel like students can handle a basic poem and some analysis questions. Try out a formative. I purposely choose simple questions or create questions that don't require much knowledge of specific poetic terms yet. I like to have the students start out just enjoying poems and answering questions about overall meaning before asking for specific metaphors, purposes of similes and the like. You can use Free as a... as a possible formative, but feel free to pull in any formatives you have or have created with your team or district.
While students are working, I'll be moving around to monitor. This shouldn't take them very long, as there are only 5 questions. Here are some things you may see.