We have developed and evaluated a set of tutor construction tools which enabled three computer-naive educators to build, test and modify an intelligent tutoring system. The tools constitute a knowledge acquisition interface for representing and rapid prototyping both domain and tutoring knowledge. A formative evaluation is described which lasted nearly two years and involved 20 students. This research aims to understand and support the knowledge acquisition process in education and to facilitate browsing and modification of knowledge. Results of a person-hour analysis of throughput factors are provided along with knowledge representation and engineering issues for developing knowledge acquisition interfaces in education.