The aim of this article is twofold. First, the final results of two research projects, which investigated the impact of Information and Communication Technology (ICT) on primary schools teachers in disadvantaged areas in Brazil (BET k-12) and South Africa (MELISSA), are presented and discussed. Second, the Self-Efficacy construct is proposed as a tool to measure how teachers' perception of being able to use technology (CSE--Computer Self-Efficacy) affects teachers' perception of being an effective teacher (TSE--Teacher Self-Efficacy). This article intends to provide data gathered from two case studies in which the Self-Efficacy construct has been applied to measure the impact of ICT in teaching experiences. One out of four surveys confirmed the hypotheses of the above mentioned projects, namely, an increased CSE caused by the improvement of technological skills and a correlation between CSE and TSE. Hence, the authors considered the possibility of creating a new tool to better understand the impact of ICT on teacher training through Self-Efficacy.