Science teachers often have two different curricula--the ideal framework on paper and the real, day-to-day instructional program that occurs in the classroom. A number of factors can affect how much of that ideal framework is accomplished. For example, how a facility is designed and how space is used can affect student achievement, classroom safety, and teacher liability. When science teachers and administrators plan and design classroom environments, they should consider four factors that play a major role in classroom efficiency and safety: student-teacher ratio, student-space ratio, facility layout, and storage space. This article presents a review of these topics and provides suggestions for how teachers can make use of their existing classroom space.