This overview of substitute teaching in K-12 schools looks at why substitutes are needed, factors that attract individuals to the work, and what school administrators can do to facilitate good substitute teaching. While schools continue to utilize substitutes for traditional reasons such as personal or family illness or emergency, the school reform movement of the mid-1980s has involved classroom teachers in a variety of nontraditional, noninstructional activities. In addition, changes in federal or state labor laws may result in teachers being eligible for more personal and sick leave. Individuals work as substitute teachers to earn income, but primarily to gain experience and make contacts that may lead to permanent, full-time teaching positions. To structure good substitute teacher programs and create a dependable cadre of replacement teachers, school administrators can hire permanent, full-time substitutes, institute graduated pay scales, offer inservice training, provide feedback, improve recruitment procedures, develop and provide a substitute teacher's handbook on school rules and policies, see that substitutes receive improved lesson plans, and appoint a district substitute teacher coordinator. (Contains 10 references.) (LL)