During the COVID-19 pandemic and ensuing lockdown in which schools were physically closed, parents often had to increase their involvement in their early adolescent children's schooling. The present study examined the relations between young people's perceptions of parental involvement (support, structuring, competence, conflict, unwanted help, and punitive control) with remote schoolwork effort over time during the first lockdown in England. Furthermore, we examined whether schoolwork motivation (expectancy and value beliefs) mediates the relation between parental involvement and schoolwork effort. Ninety-eight UK secondary school students in School Years 7-9 participated in this 5-week weekly diary study. Data were analysed using multilevel models. At the between-person level, parental support, parental structuring, and parental competence were positively associated with schoolwork effort (mediated by expectancy and value beliefs in English), whereas conflict, unwanted help, and punitive control were negatively associated with schoolwork effort (mediated by expectancy in English). At the within-person level, parental competence was positively associated with schoolwork effort, and no indirect effects were found. Parental involvement may be more important in schoolwork motivation and effort in understanding differences between individuals than how the same individuals change over time.