Let the children explore different shields to see what they looked like, and what the symbols on the shields represented. Print out or copy pictures of different shields to hand on the walls. Look at the book "Coat of Arms" by Catherine Daly-Weir and Jeff Crosby to see a wide variety of shields and to learn the history and significance of shields.
Once the students understand the concept of the shields and the designs on the front of the shields, have them design their own shields on paper. They can chose the shape of the shield, the design, and the colors used in the shield. Encourage the students to be creative when making their shields.
The book "Design Your Own Coat of Arms: An Introduction to Heraldry" by Rosemary Chorzempa provides instructions on how to design a shield, as well as a history to the different lay-outs and common symbols. This book may help students who are unsure of what to do.
Create an actual shield out of foam board, Styrofoam or cardboard. Use paints to paint the shield design on the front. Staple a couple straps of material to the back for the students to slip their arms through and wear their shields.
For fun, hold a jousting tournament. Knights used their shields to protect themselves while jousting. The students can use the shields they created to protect themselves, and pool noodles as jousts.