Barriers to well-being detract from teachers' effectiveness, however there is limited understanding of exactly how this occurs. We explored whether fourth grade teachers' (N=65) burnout symptoms related to their lesson length in mathematics, science, and English Language Arts, and to time in each of three classroom groupings. Multiple regression revealed a negative association between depersonalization and time in science, and revealed that teachers experiencing more burnout spent less time in whole-class and small-group configurations which require their direct involvement, and more time in independent work which does not. Findings can inform supports for teachers experiencing burnout which target instructional practices. [This paper was published in "Teaching and Teacher Education" v156.]