Appropriate shoes and a hard surface to tap on. I use a board of wood, but you can use any hard surface.

Tap shoes are recommended. Students may use flexible sneakers (with laces tied tightly).
Please make sure your child takes the class in an open area where they will not accidentally kick something or put themselves in danger. Ideally, the space would not be slippery, but if it is a slippery surface, it is recommended to use non-stick socks or shoes. Parents and guardians should remain nearby to assist and prevent accidents. 
Having a water bottle nearby is ideal. If class is taken during warmer months, it is ideal to have an air conditioner or fan running to prevent overheating.