Schools in China and elsewhere are starting to teach English as a second language or foreign language (FL) to students at increasingly earlier ages. Although young learners (YLs), due to their developmental stage, are likely to be particularly susceptible to the influence of parents, parents' roles in YLs' motivation to learn English as an FL is not well understood. Moreover, we don't fully understand why YLs lose their motivation to learn English by their upper elementary school years. Using self-determination theory, this study examined how parents' socio-economic status (SES) and behaviours and beliefs about their children's English education influenced children's motivation to learn English in China. The participants were 198 fourth-, 191 sixth- and 183 eighth-grade students and their parents. Data were gathered using a series of surveys distributed to all the students and their parents, as well as interviews with 96 focus group students. Parents had substantial but varying influences on their children's motivation, depending on their SES backgrounds and their children's grade level. Whereas higher SES parents adjusted their behaviours according to their children's changing needs, lower SES parents tended to remain controlling and often failed to foster their children's self-competence and self-determined motivation. Higher SES parents' abilities to provide their children with greater opportunities to use English outside of school were increasingly advantageous for the children's development of self-determined motivation as their grade level increased.