We have read 6 poems, and I think students' poem reading has advanced to a certain stage that I don't need to comment on each student's performance on “When I am One-and-Twenty.” However, poem reading is a chance to understand the importance of the voice, which carries much more information than printed matters do.
I want you to read slowly because the priority in reading is to read each word right. Reading slowly is very important to correct word pronunciation. You will have less chance to understand your flaws and correct yourself if you read too fast.
After you are comfortable with your word pronunciation, read a poem like you are telling a story to your audience. Your audience will not find your story interesting unless you show passion first. The content of a text does matter, but the way the content is delivered matters even more.