The aim of the current research is to develop achievement, deep understanding and social adaptation among second-year high school students through the presentation of a proposed unit in sociology based on the Progressive Inquiry Model, To achieve this objective the researcher built the proposed unit on contemporary social problems, and prepared a teacher's guide for guidance during the teaching of the topics of the proposed unit according to the progressive inquiry model. It also required the preparation of the following research tools: (achievement test to measure students' achievement in the topics of the proposed unit - deep understanding test - social adaptation scale). The research sample consisted of an experimental group comprising (30) male and female students in the second year of high school in one of the schools affiliated with the Minya El-Qamh Educational Administration. The results indicated statistically significant differences at a significance level of (0.01) between the means of the grades of the students in the experimental group in the pre and post applications of the achievement test, the deep understanding test, and the social adaptation scale as a whole and in the sub-dimensions individually in favor of the post-application, indicating the effectiveness of the proposed unit based on the progressive inquiry model in developing achievement, deep understanding, and social adaptation among the research sample.