In this era, society needs young students to think and do what they should do in the 21st century. This research aims to promote reasoned argumentation in science for lower secondary students, which is relevant to prepare citizens in a world of change. The participants in this study were 33 lower secondary students. The findings found that instructional practices which promote reasoned argumentation as "CRABS MODEL"; they are choosing issue; reasoning; argumentation; brainstorming and summary. This can make students have higher thinking in argumentation. Students could develop the reasoned argumentation by using problem analysis process, data gathering and reasoning, facts and opinions classification through argument, brainstorming of various choices and summary, which are higher than pre-test at the statistical significance level of 0.05.