Students are often reluctant to practice using characterizations. Ask them to overemphasize them during this exercise. If you exaggerate them while practicing it is easier than to tone it down when you actually present the poem. It is very difficult, though, to effectively portray a character's voice when you have only practiced it silently or without much emotion or drama. Where My Clothes Are Dirty clothes should be put in the hamper.
Clean clothing belongs in the drawer.
Have students pair up and practice reading the poem to each other. Have them read the first two lines in the following voices, followed each time by the last two lines in their own voice. A. Their own mother or father. B. A really mean or strict person. With an accent of their choice.