Transformational grammar offers the most adequate system by which to meet the goal of grammar instruction, which is to increase the student's understanding of the nature of language. This grammar attempts to explain the mental processes underlying the production and understanding of sentences, to describe linguistic competence, to construct linguistic descriptions of particular languages and a theory of the nature of language, to distinguish between grammatical and ungrammatical sequences, and to judge how well it is fulfilling its tasks. The teaching of transformational grammar, which can begin formally with seventh-graders, offers many possiblities for student involvement in genuine linguistic problems--examination of the constituents of sentences, the relationship between deep and surface structure, the relationships between sentences, and the principles of transformations. (JS)