Find 10 to 15 different hand-sized props, such a plastic medieval shield or a fake bouquet of flowers, that you will use for this activity. If your school has a drama class or even an auditorium, you may be able to acquire some props you can borrow there. If not, try checking local thrift stores for toys or other inexpensive items that can easily stand in for more conventional props.
Split your class into groups of two and give each group a prop. Present the class with the theme or subject area that you will be covering in your next unit: for example, a unit on cells in a biology class. Instruct students that each pair will write and eventually act out a two-minute skit about the topic using the prop as a key element. For younger students, you may want to match the props to the topics to give students an easier time of figuring out how to use them in sketches.
Explain to students that the point of the skit is for them to show you, the teacher, what they already know about the topic that you will be covering throughout the next unit. This means that they do not need to use their books or any other outside sources to write their sketches with, just what they already know. However, inform students that they will still receive a grade for this skit that will reflect the level of effort they put into it. Also point out that they should use their prop as the starting point for writing their skit.
Give your class a day or two to work on their skits, and have them present them in class. After each pair performs, ask them how their prop gave them the idea for their sketch. After everyone has gone, ask students how they liked this activity and whether they would like to try a similar one in the future. This is a useful question, because it will help you determine the best kinds of lessons to use in the unit for your individual class.