This paper investigated the effect of teacher quality, represented by teacher level characteristics, on mathematics gain scores employing a three-level hierarchical linear model (HLM) through value-added model (VAM) approach. The analysis investigated significant predictors at student, teacher, and school levels for predicting students' gain scores and also estimated d-type effect sizes at teacher and school levels. We found the significant effects of teacher's mathematics content certification, teacher experience, and the interaction effects of mathematics content certification with student level predictors. Although school poverty significantly predicted students' gain scores, the school level effect was relatively small.