This resource from NASA/JPL's Night Sky Network includes a full description of the activity and materials needed to demonstrate how both lunar and solar eclipses occur. The printable document provided includes instructions for engaging students, and questions to ask in leading the discussion.
Materials for each group of 3-4 students are:
- Yard (or meter) stick
- 1" ball (for the Earth)
- 0.25" ball (for the Moon)
- two toothpicks
- two binder clips
Alternatively, this setup can be done as a teacher-led demonstration.