The discussed and illustrated principles regarding teacher performance data and decision making are common sense ideas that have been developed based on a good deal of thought about the definition of minimally acceptable job performances. The presented scoring systems are ways of describing how much a teacher must do in order to be scored positively, i.e., certified or continued in employment. The purpose of the assessment should be considered when the decision-making structure is planned. Since the pattern and nature of the requirements will certainly influence the demands that will be put on the teachers, developers of performance assessment systems would do well to consider how many criteria, categories, and sub-categories a teacher can fail to demonstrate, and still be called acceptable. Generalizability procedures can help determine the effect of alternative procedures, such as varying number of raters, occasions, or items. Whole scores may be more defensible for certification but inappropriate for staff development. (PN)