Presented are the results of a 2-year study on achievement patterns in 917 educable mentally retarded (EMR) children (8.0 to 19.11 years old) in the district run classes throughout Montgomery County, Pennsylvania. Described are the student participants, as well as the teachers and districts from which they came. Also discussed are the test devices (certain levels of the Stanford Early School Achievement Test and Stanford Achievement Test) and testing procedures used. It is noted that selection of test levels was done on a current-level-of-functioning basis rather than on chronological age (an approach known as out-of-level testing). Sections also cover the item analysis framework, sampling, raw data results, interpretation of results for each year, and discussion and recommendations. Noted among findings is that teachers of EMR children were fairly accurate judges of the current functioning levels of their students. The bulk of the document consists of appendixes which include correspondence, raw data results, and selected responses to the evaluation form. (SBH)