Elementary school students experience significant personal changes; their bodies change, as well as their inner selves. Their emotional status can be affected by both intristic and extrinsic factors; therefore, it is vital to highlight the emotional factors that influence the learning process, as a negative emotional status may lead to reduced motivation and low school performance, whereas a positive one may bring the opposite results. The aim of this study is to evaluate the effects of the teaching process onto the students’ emotional status, and how it affects their academic performance. The study was conducted on 15 3rd-grade elementary school students in Greece. The students’ scores on weekly reviewing tests were used, in the subjects of Language, Math, History, and Environmental Study. The affective state of the students was measured by the AffectLecture app of the AUTh Medical Physics lab. The results indicate that after attending the Environmental Study class, students have a more positive emotional status; on the other hand, this wasn’t the case with the other subjects. Additionally, the students’ emotions and their test marks, exhibit a strong positive correlation. These findings suggest that the affective state of students and how it alters should be taken into account by education professionals, researchers and policy makers.