The relationship between 2nd and 3rd grade teachers' linguistic knowledge and spelling instructional practices and their students' spelling gains from fall to spring was examined. Second grade (N = 16) and 3rd grade (N = 16) teachers were administered an instructional practices survey and a linguistic knowledge test. Total scores on the two instruments were not significantly related (r = 0.20), indicating two different constructs. Students (N = 331 2nd graders, N = 305 3rd graders) completed a 40 item spelling dictation test in the fall and spring. HLM analyses were conducted on subsamples of weaker spellers (Ns = 226 2nd graders and 50 3rd graders) who spelled fewer than 20 words correctly on the pretest. Limiting the sample to weaker spellers eliminated ceiling effects on pre- to posttest gains. Results revealed that 2nd grade teachers' linguistic knowledge of phonemic units in words, their teaching of spelling strategies, the time they spent in weekly spelling instruction, and the greater the number of weaker spellers in their classrooms, were significant predictors of weaker spellers' improvement in spelling. For 3rd grade teachers, HLM analyses were not significant perhaps due to lack of power. However, 3rd grade teachers' phonemic knowledge was significantly correlated with weaker spellers' gain scores. Results while correlational provide tentative support for the conclusion that teachers who are more knowledgeable about phonemes in words and who utilize more effective, research based spelling instruction are more successful in teaching spelling to weaker spellers.