A study was designed to identify highly teachable composing skills that have a strong statistical relationship with composition quality across various grade levels. Sample compositions were randomly selected from the National Assessment of Educational Progress (1972). A total of 750 compositions written by 9-, 13-, and 17-year-old-students (250 for each age level) were analyzed using 43 indices. The five skills that were identified were modification within sentences, subordination between sentences or paragraph development, vocabulary, sentence sense, and usage. The first three skills can be taught by having students rewrite their compositions with specific suggestions from the teacher as to sentences that should be combined or expanded to foster modification within sentences, sentences that should be added to foster more depth of modification between sentences, and words that should be changed to foster more variety of vocabulary. The other two skills can be taught and reinforced by using exercises from currently existing grammar and composition texts. Objective and easily calculated indices were used to measure the skills, and a procedure for establishing minimum competency levels for the skills was applied. (MKM) Aspect of National Assessment (NAEP) dealt with in this document: Results (Secondary Analyses).