Physics, as a foundational science, has particular importance in predicting the postsecondary success of students who major in science, technology, engineering, and mathematics. This large-scale study examined teacher-level and school-level predictors of student performance in physics, with a focus on isolated or "lone-wolf" teachers. The study analyzed data from 1,584 high school physics teachers representing 960 public schools, and data from 47,734 students in the academic year 2016-2017. Teacher-level variables included the content preparation and certification of teachers, physics course load, years of experience, whether the teacher taught other STEM courses, and whether the teacher was "isolated" (i.e., the only person teaching physics at that school). School-level variables included standardized test pass rates, school size, socioeconomic status, locale (urban, suburban, or rural), and ratio of students taking physics courses. Results indicated a significant proportion (40%) of physics teachers were isolated, and their students tended to have weaker physics performance scores than students of nonisolated teachers. Compared to the nonisolated teachers, a larger percentage of isolated physics teachers were uncertified in physics and taught in urban and rural schools, and urban teachers had less teaching experience than suburban and rural physics teachers. When analyzing the subset of isolated teachers, the research indicated that urban locale and school socioeconomic status were the main negative predictors of student physics performance. By contrast, years of teaching experience was the a significant positive predictor of student success.