To investigate the assertion that there is a tendency for teachers to emphasize skills already mastered by their students, data were collected on 488 seventh grade mathematics students in three junior high schools. Of these, 285 were assigned to experimental classes taking the curriculum under development and 203 were assigned to comparison classes providing the regular mathematics curriculum. The students were average in intelligence, but were at least 1 year behind in mathematics achievement. The main testing instrument was the Diagnostic Test with which the students were both pre- and posttested. Relevancy ratings were collected to check on the fairness or appropriateness of the test items. The results showed that (1) teachers selected instructional objectives that reflected skills already available to their students, and (2) experimental teachers tended to gear instruction to skills already achieved by students at entry into the program. Two implications are drawn: (1) With regard to instructional practice, teachers need to be informed about the entry skills of their students as related to the objectives of a course of instruction; and (2) data on entry skills could have been most useful to teachers developing the program had they been made available early in the research. (HW)