Children in grades one to four completed two sentence construction tasks: (a) Write one complete sentence about a topic prompt (sentence integrity, Study 1); and (b) Integrate two sentences into one complete sentence without changing meaning (sentence combining, Study 2). Most, but not all, children in first through fourth grade could write just one sentence. The sentence integrity task was not correlated with sentence combining until fourth grade, when in multiple regression, sentence integrity explained unique variance in sentence combining, along with spelling. Word-level skills (morphology in first and spelling in second through fourth grade) consistently explained unique variance in sentence combining. Thus, many beginning writers have syntactic knowledge of what constitutes a complete sentence, but not until fourth grade do both syntax and transcription contribute uniquely to flexible translation of ideas into the syntax of a written sentence. In Study 3, eleven syntactic categories were identified in single- and multi- sentence composing from second to fifth grade. Complex clauses (independent plus subordinate) occurred more often on single-sentence composing, but single independent clauses occurred more often on multi-sentence composing. For multi-sentence text, more single, independent clauses were produced by pen than keyboard in grades 3 to 7. The most frequent category of complex clauses in multi-sentence texts varied with genre (relative for essays and subordinate for narratives). Thus, in addition to syntax-level sentence construction and word-level transcription, amount of translation (number of sentences), mode of transcription, and genre for multiple sentence text also influence translation of ideas into written language of child writers. Results of these studies employing descriptive linguistic analyses are discussed in reference to cognitive theory of writing development.