The security and assurance of our computing infrastructure has become a national priority. To address this priority, higher education has gradually incorporated the principles of computer and information security into the mainstream undergraduate and graduate computer science curricula. To achieve effective education, learning security principles must be grounded in experience. This calls for effective laboratory exercises (or course projects). Although a number of laboratories have been designed for security education, they only cover a small portion of the fundamental security principles. Moreover, their underlying lab environments are different, making integration of these laboratories infeasible for a semester-long course. Currently, security laboratories that can be widely adopted are still lacking, and they are in great demand in security education. We have developed a novel laboratory environment (referred to as SEED). The SEED environment consists of Minix, an instructional operating system (OS), and Linux, a production OS; it takes advantage of the simplicity of Minix and the completeness of Linux, and provides a unified platform to support a rich set of laboratories for computer security education. Based on the SEED environment, we have developed a list of laboratories that cover a wide spectrum of security principles. These labs provide opportunities for students to develop essential skills for secure computing practice. We have been using these labs in our courses during the last five years. This article presents our SEED environment, laboratories, and evaluation results.