Within the field of computer assisted language learning (CALL), scant literature exists regarding the effectiveness and practicality for secondary students to utilize data-driven learning (DDL) for vocabulary acquisition. In this study, there were 100 participants, who had a mean age of thirteen years, and were attending an international school in Ho Chi Minh City, Vietnam. This particular milieu unsurprisingly comprised "third culture kids" (TCKs) and "cross-cultural kids" (CCKs). They were assigned to a control and experimental group; both had several intensive weeks of online-dictionary learning training, while the experimental group also experienced intensive DDL training. This was done prior to the start of the eight-week longitudinal study. Major findings included a significant longitudinal main effect for both groups, significantly overall higher results for the experimental group than the control, and a significant difference among subjects' grade level was discovered. Furthermore, the experimental group exhibited a significantly marked increase in vocabulary results in the later weeks of the experiment. In general, these results show that DDL can be successful in the secondary school English as a foreign language (EFL) context and that it promotes significantly better vocabulary acquisition when used in conjunction with online-dictionary vocabulary learning methods, especially for a sustained longitudinal period of time.