This study examines how interactions in class WhatsApp groups impact students' motivation and academic achievements. The research incorporates both qualitative and quantitative analyses to explore associations between various types of interactions and academic performance. Key findings reveal a strong positive correlation between students' motivation and the volume of affective-emotive messages, especially those from teachers. While cognitive-analytic interactions did not significantly predict higher academic achievement, qualitative interviews highlighted the need for more educational content in WhatsApp groups, such as exercises. The study also found a positive, albeit weak, association between classroom climate and interaction patterns. However, an interesting inverse relationship emerged between socioeconomic status and the prevalence of affective-emotive messages. The research emphasizes the importance of incorporating affective-emotive interactions in educational settings and recommends expanding the use of WhatsApp groups as an effective supplementary platform for fostering motivation and improving academic achievements.