Since scientists use argument to validate ideas, students should also engage in argument using evidence to develop their scientific understandings. Students engage in argumentation when they make claims and defend those claims with evidence and/or reasoning as part of both oral and written discourse. However, this type of argumentation does not match the typical classroom discourse pattern nor is it language with which students are familiar. We recognized that our students were writing and talking about what they did in science, but struggled to develop an argument. Based on this, we created a study group with others at our school to discuss ways in which we could support argument among our students. We share what we learned and how we worked with second graders to develop evidence-based argumentation within their science notebook entries and in science talks. First, we worked with students to support them in understanding the expectations and language of argument. Then we provided them with opportunities to practice identifying and working with the skills of arguments. We provide examples of student work and dialogue to support these ideas.