This study developed a platform, entitled Parent–Teacher-Ark, to support parental engagement in their children’s education, and investigated parents’ online behaviors and perceptions in the platform. This platform consisted of the home–school communication bulletin, the parent–teacher forum, the online parental learning courses (OPC), and the multiple e-Portfolio (MeP) in order to explore the potential of digital technology for helping parents and teachers co-work more closely. This study was conducted in a digital school, in which more than 90% of parents prepared tablet PCs for their children. There were 653 parents of the first to third graders participating this study, which aimed to investigate parents’ using behaviors, perception and thoughts by system records, questionnaires, and interviews. The results indicated that the participations of the parents gradually increased and they had positive perceptions toward OPC, and MeP (in particular, learning traffic signals and visualized learning profile). The results suggested that most parents thought that the Parent–Teacher-Ark platform may help them increase their educational knowledge and understand children’s learning.