Most educational objectives can be classified as either mastery or developmental. For mastery objectives, teachers can develop satisfactory assessment instruments relatively easily and can describe student achievement as "can do" or "can't do." For developmental objectives, there are a number of evaluation methods, and student progress varies in attaining these objectives. An adequate description of achievement of these developmental objectives requires a set of reference points to identify stages of development. Teachers develop a sense of these criteria by considering the instructional materials and the performance of various groups of students. Standardized achievement tests may help the teacher assess students' levels of development. Describing student's performance in an educational program requires an assessment of what the student "can do" and an educated estimate of the student's progress in meeting important developmental objectives. (Author/MH)