This longitudinal study explored the ways parents’ and teachers’ expectancy for success influences 3rd–5th children's expectancy for success and achievement in science. Guided by an open‐systems perspective and functional (Ballantine & Roberts, 2007) and expectancy‐value (Eccles, 2005, 2007) theories, we focused on school related socialization processes and the role of parents and teachers in shaping children's abilities and skills. Participants included 153 children from 23 rural, Oklahoma schools and provided matched sets of parent, teacher, and child surveys. Weisgram and Bigler’ (2006) science self‐efficacy subscale organized survey items where wording changes allowed parallel parent and teacher versions of the scale. Achievement was determined by test scores on the state‐administered Oklahoma Core Curriculum Tests (OCCT). Results showed teachers’ expectancy for children's success in science did not significantly predict students’ fifth grade science achievement. However, regression analyses showed parents’ expectancy did predict students’ fifth grade science achievement. The relationship was statistically significant and explained about 19% of the variance in fifth grade science achievement test scores (R2 = 0.19). We further determined that children's science self‐efficacy significantly influenced science achievement scores (β = 0.20) (however, this was a far weaker influence than the direct effect of parents’ expectancy [β = 0.38] of children's success in science). The novel finding is that parents have an influence on children's achievement over and above children's own self‐efficacy beliefs about science. Clearly, parents matter when it comes to science achievement. Though it seems parents are more influential than teachers when it comes to children's own expectations and achievement success in elementary science, we encourage further consideration of parent expectancy as it relates to child ability and achievement, modified classroom strategies, and home–school relations to better align teachers’ positive influence on children's expectancy for success. © 2016 Wiley Periodicals, Inc. J Res Sci Teach 54:693–712, 2017