An instrument to help teacher supervisors in El Salvador to identify and measure good teaching was developed and tested. Because the supervisors were not trained as researchers, they needed an instrument that was simple to use as well as reliable. Several indicators were defined to distinguish between modern and traditional teaching methods, for example the ratio of discussion time to lecture time, the ratio of opinion and thought questions to memory questions, the use of learning aids, and the amount of time spent by students on projects of their own choosing. These were measured on a classroom observation form made up of 33 categories. Each category was divided into segments of class time. The completed form records the number of minutes the teacher spends at each activity--dictating, writing at the blackboard, reviewing individual projects, and the like. Approximately six hours were needed to train teacher observers to use the forms. The instrument was tested and proved effective. (MG)