The evidence that teachers’ short-term instructional effects correspond to substantial long-run impacts on students’ lives provides much of the impetus for a wide range of educational reforms that are focused on identifying and responding to differences in teachers’ value-added effectiveness. However, relatively little research has examined the mechanisms by which the particular knowledge or skills that teachers impart to students contribute to their longer-term success. In this paper, we investigate the persistence of teachers' value-added effects on student learning over multiple years and across subject areas. We find that the long-term instructional effects of English Language Arts (ELA) teachers are substantially more generalizable across subjects than the instructional effects of math teachers. Moreover, we find that this pattern of differential cross-subject ELA teacher effects is consistent across two different state testing regimes and district contexts. In comparison to math teachers, ELA teachers' impacts on student achievement appear to represent more broadly applicable skills that support student learning across disciplines. Our results highlight the potential for important variation in the quality of teacher-induced learning, distinct from the relative size of learning effects as measured by short-term student achievement outcomes.