This report describes the general plan for a study to clarify the interpretation of group performance measures of student achievement. Group tests are the most efficient procedure for collecting achievement information from a large number of students, but they also require item formats that may be different from the form in which students normally demonstrate or apply their learning. To provide information about some of these potential differences to be used in the interpretation of group scores, two studies are planned, one of second grade students in the areas of reading and mathematics, and one of second and fifth grade students in reading comprehension. (MJB)