Academic misconduct is common in both secondary and higher education and schools still lag behind in preventing unethical behavior. The present research addressed the effectiveness of formative activities aimed at improving ethical behavior of students in secondary education. The probability of engaging in cheating, harming others, hiding information, and theft was assessed before participants were provided with information about ethical and unethical behavior and engaged in group activities in the classroom. The comparison of pre- and postintervention scores showed that those students with a higher probability of engaging in unethical behavior were less inclined to cheat and hide information, whereas the students who behaved ethically reported a greater probability of engaging in all four unethical behaviors. The implications of interventions based on information and group discussions, as well as the challenges of future interventions on ethical behavior, are discussed.