Background/Context One important question to educational research is whether teachers can influence student achievement over time. This question is related to the durability of teacher effects on student achievement in successive grades. The research evidence about teacher effects on student achievement has been somewhat mixed. Some education production function studies seem to suggest that the effects of observed teacher characteristics on student achievement are negligible, while others suggest that they are considerable (Greenwald, Hedges, & Laine, 1996; Hanushek, 1986). Other studies have consistently documented that teachers differ substantially in their effectiveness measured as between-classroom variation in achievement adjusted by student background (Hanushek, 1986; Nye et al., 2004; Rivkin et al., 2005). Thus far, there is no evidence about the persistence of teacher effects in early grades using high quality data from a randomized experiment. Purpose/Objective/Research Question/Focus of Study This study examines the enduring benefits of teacher effects on student achievement in early elementary grades using high quality experimental data from Project STAR. I am interested in determining the persistence of teacher effects in early grades and whether teacher effects remain strong predictors of student achievement or fade over a four-year period for kindergarten through third grade. Research Design I computed teacher effects as classroom-specific random effects and then I used them as predictors of student achievement in subsequent years. I also examined whether teacher effects persisted through third grade. Multilevel models were used to conduct the analysis. The results suggest that overall teacher effects in early grades are evident through third grade in reading and mathematics achievement. Findings/Results The findings support the idea that teachers do matter and significantly affect reading and mathematics achievement not only in the current or the following year, but in subsequent years as well. However, the results also show that teacher effects estimates in previous grades are smaller than estimates in later grades. The teacher effects are more pronounced in reading. Conclusions Students who receive effective teachers at the 85th percentile of the teacher effectiveness distribution in three consecutive grades kindergarten through second grade would experience achievement increases of about one-third of a SD in reading in third grade. These effects are considerable and comparable to achievement increases caused by cumulative effects of small classes in early grades. Such effects in education are important and are nearly one-third of a year's growth in achievement (Hill, Bloom, Black, & Lipsey, 2008).