The purpose of the study was to assess early literacy skills and examine the presence and stability of challenging behaviors across the critical threshold of the kindergarten school year. Students' (n = 337) literacy performance (letter sound fluency, word attack, and phonological awareness) and challenging behaviors (teacher ratings of inattention/hyperactivity, mood/affect, and defiance/aggression) were measured in the fall and spring. Changes in student behaviors were classified as (a) "Elevated Stable," (b) "Average Stable," (c) "Increased," or (d) "Decreased," based on the relation of scores to normative and clinical cutpoints, and to changes observed from fall to spring. Students' literacy growth patterns varied by type of behavior. In terms of defiance/aggression, students classified as "Decreased" demonstrated the strongest growth. By contrast, the level of challenging behavior was most relevant for inattention/hyperactivity, and behavioral stability was most relevant for mood/affect. After describing major implications, limitations and directions for future research are discussed. [This paper was published in "The Elementary School Journal" v120 n2 p220-242 2019 (EJ1234503).]