The Edmonton Grade III Achievement: 1956-1977 study is a comparison of achievement in reading, arithmetic, and language involving all of the third grade students in a large school system. Six basic skills tests which were administered to all of the Edmonton third grade students in 1956 were reprinted and administered to all of the third grade students in Edmonton in 1977. Seventeen items were deemed inappropriate because of changes occurring since 1956; they were eliminated from the analyses. The remaining test items and procedures used in 1956 were duplicated as closely as possible in 1977. The six tests were: the Gates Word Recognition Test, the Gates Paragraph Reading Test, the reading, arithmetic and language sections of the California Achievement Tests, and the California Mental Maturity Test. The 1956 tests were rescored and item by item results for each student for each test were recorded. Although arithmetic scores declined from 1956 to 1977, the 1977 third graders scored higher in spelling and in general scholastic ability than their counterparts in 1956. Extensive item analyses and subtest score comparisons for males, females, and both sexes are included as well as test items and information for principals and teachers. (Author/JAC)