This study investigated kindergarten, first, and second grade children's ability to make linguistic judgments about sentneces that were either correct or disrupted along semantic or grammatical lines. Sentences on the judgment task were created according to clearly specified rules utilizing grammatical features that could be transformed into predetermined ungrammatical forms. Children listened to sentences said by a puppet and judged whether the puppet said the sentences the right way or the wrong way. The data were analyzed for developmental trends and the effects of different aspects of disruption on judgments. The relationship of performance on each type of sentence to reading achievement was also investigated for first and second graders. The results indicate that the ability to make judgments about the acceptability of sentences is developmental in nature. The type of disruption has an effect on performance. Performance on all three sentence types is related to reading achievement at first grade, but only performance on grammatically disrupted sentences remains related at second grade. The results are interpreted to indicate that performance on correct and semantically disrupted sentences reflects a linguistic maturity related to reading achievement at first grade. (Author)