Three studies were carried out with Compulsory Secondary Education students to verify the effectiveness of two intervention methods--the infusion method (IM) and the instrumental enrichment program (IEP)--to enhance thinking skills, creativity, behavioral self-regulation, and academic achievement. Study 1 (N = 118) was conducted in order to create the IM, an instruction method designed to teach these skills along with the syllabus content, and to compare its effects with the conventional method (CM). In Study 2 (N = 176), the effects of the IM, the IEP, and the CM were compared in the same variables. In Study 3 (N = 168, using the same subjects as in Study 2), the effects of the IM and the IEP were analyzed to determine whether they were maintained or they increased with time. The results showed that greater changes were obtained with the IM than with the IEP in all the criterial variables and that the effects attained in Study 2, in addition to being significant, persisted at least 1 year after completing the intervention. Relevant scientific and educational implications are drawn from the studies. (Contains 4 tables.)