This article reports on an inquiry of a teacher evolution project informed by systemic functional linguistics and its affect on student writing in math and science. The inquiry was conducted with 41 teachers from urban and rural schools enrolled in the project at a university in the US. Data, in the form of survey, interview, instructional planning, classroom observation, and student writing at divers stages of teacher evolution, were assayed to display affect of the teacher evolution. The findings point out that teachers need a functional linguistic viewpoint to ameliorate their pedagogical practice for teaching writing. A functional approach to teacher evolution affects not only growth of teachers’ knowledge and skills but also students’ writing performance in the areas of math and science.