Attention Deficit Hyperactivity Disorder (ADHD) is raising concerns across health systems, affecting about 5% of the school-age population. Therapy usually involves psychostimulants, which are prone to adverse drug reactions (ADRs). Teachers have many contact hours with children and can easily detect behavioral changes upon the beginning of medication. However, few studies have focused on the role of teachers in the management of ADHD children and detection of ADRs. The present work aimed to characterize the perception of primary school teachers regarding the impact of ADHD therapeutics. A questionnaire was constructed focused on teachers’ training regarding ADHD and its therapy; experience with students with ADHD; changes upon beginning of medication; and observation of ADRs. A total of 107 completed questionnaires were obtained. The results indicate that more than 40% of the inquired teachers have received training in ADHD, but in most cases, the theme of therapeutics was absent from that training. The vast majority of teachers (91.6%) have had students with ADHD and observed mood alterations associated with medications. More than 60% of the teachers answered that they are aware of the ADRs and of these, 24% have already detected them in their students. The teachers reported the observed ADRs to parents in 93% of the cases and to doctors in 28% of the cases. In conclusion, the results show the need to reinforce teachers’ training in ADHD and its therapeutics.