This study seeks to question what impact the intervention of an educational voucher has had on the process of school choice. The context examined in this study is the Pre primary Education Voucher Scheme (‘Voucher Scheme’) in Hong Kong. Using a Straussian grounded theory method, data collected from 40 parent interviews are coded, analysed, and developed into categories. A critical realist perspective is adopted for scrutinising the categories and for making inferences about their properties and relationships. Conceptualisation of these categories and of their properties and relationships formulates a grounded theory of school choice under the intervention of the Voucher Scheme. The theory generated in this study centres around parents as choosers, with their actions being sensitive to conditions and to contexts. This study finds the sophistication and capacity of parents making school choice decisions to be influenced by these parents’ resources and how motivated they are, as causal conditions. The significance of causal conditions is mediated by contextual conditions and by intervening conditions. As illustrated in this study, the most important contextual condition is a family’s socioeconomic status. The primary intervening condition at work is the Voucher Scheme. The interactions of these conditions play a significant role in shaping parents’ school choice actions and, therefore, in respective outcomes. Nonetheless, these conditions inform but do not determine school choice decisions; because parents, as social agents, deliberate reflexively and act strategically when choosing kindergartens for their children. This study has found that the Voucher Scheme does not result either in clear-cut implications for the empowerment of parents or in their social segregation. Rather, there are multifaceted effects which occur, and these effects vary between parents. Likewise, the Voucher Scheme represents not marketisation per se but the transformation of the market into two distinct segments, of which one segment has become increasingly regulated.