Research conducted over several decades indicated directed forgetting as an useful method for studying inhibitory mechanisms in cognition. Cognitive inhibition is an important ability in problem solving and reasoning. There are two distinct experimental procedures of directed forgetting. In the list procedure, participants are presented two list o words (1 and 2) for study and an instruction to either forget or remember follows the presentation of list 1. An instruction to remember follows the presentation of list 2. When asked to remember the words from both lists, participants instructed to forget list 1 show very poor performance for the words from list 1 but better recall for the words from list 2, compared with those in the remember condition. The directed forgetting effects in the list method are interpreted in terms of retrieval inhibition. In the item-by-item procedure, an instruction to either forget or remember follows the presentation of each word and the directed forgetting effects are interpreted in terms of differential rehearsal. The general aim of this study is to investigate a possible relation between secondary school students’ cognitive inhibition competencies and their academic achievement. In two experiments, involving fifth and eight grade students, both experimental versions of directed forgetting tasks were used for studying this relation.