This study (partially supported by an ESEA Title III Grant) of the written composition of 190 above-average children in grades 3-6 was carried out to determine whether those children who were taught selected concepts of invention, arrangement, and style over a period of 8 months would demonstrate significant improvement in composition or sentence structure over those children who followed the typical English program. Improvement in composition was measured by five reader-rating variables--organization, style, working and aspects of phrasing, quality and development of ideas, and a total of the previous four variables. Related language growth was measured by analyzing the students' writing through the use of seven variables, part of which were based on the T-unit. Results indicated that the teaching of selected concepts of invention, arrangement, and style significantly aided growth in written composition of above-average third-grade children, with girls improving more than boys; that the experimental program did not produce significant gains in grades 4, 5, and 6; that the seven language-related variables were of little value in measuring growth in written composition; and that boys and girls demonstrated no appreciable difference in sentence-structure ability at any one grade level. (LH)