And finally, in high school:

In grades 9-12, students can investigate or analyze a system by defining its boundaries and initial conditions, as well as its inputs and outputs. They can use models (e.g., physical, mathematical, computer models) to simulate the flow of energy, matter, and interactions within and between systems at different scales. They can also use models and simulations to predict the behavior of a system, and recognize that these predictions have limited precision and reliability due to the assumptions and approximations inherent in the models. They can also design systems to do specific tasks.

—Next Generation Science Standards, Crosscutting Concept 4

Lesson idea: Ask students to select one of the Westward Expansion maps or another system example from PBS LearningMedia. Then guide them through this process:

• Describe the system they plan to study, its parts, and its boundaries. 
• Create a causal loop diagram (CLD) that shows a model of how they think its parts interact. 
• Create a stock and flow diagram that would allow them to measure or quantify some of the inputs, stocks, and outputs. 
• Identify areas of leverage—where a small change might produce a large impact, or predict the future behavior of the system based on current data.