Cyber ranges are an important tool for teaching cyber security techniques. However, setting up a cyber range for classroom use can be costly. Prior work on lowering the cost of cyber ranges focuses on open source solutions and virtual machines. Yet, these solutions do not reduce the cost of physical components-namely, the underlying hardware used to build the range. In this paper, we describe a prototype cyber range built out of Raspberry Pis, a type of inexpensive single board computer. To illustrate the functionality of the range, we use Docker and Docker Swarm to deploy a vulnerable web server across four Raspberry Pi nodes and assess it in an undergraduate classroom. Our cyber range costs under $250.00 to build and consumes less than 25 Watts of power. We open-source our materials and provide pre-built Docker images on Docker Hub to enable others to use our work. Our results suggest that cyber ranges built using Raspberry Pi clusters can lower cost and enhance cyber security education. CCS CONCEPTS • Applied computing → Education; • Security and privacy → Vulnerability management; • Computer systems organization → Embedded and cyber-physical systems.