A critical component of science is the role of inquiry and argument in moving scientific knowledge forward. However, while students are expected to engage in inquiry activities in science classrooms, there is not always a similar emphasis on the role of argument within the inquiry activities. Building from previous studies on the Science Writing Heuristic (SWH), we were keen to find out if the writing structure used in the SWH approach helped students in Year 5, 7, and 10 to create well constructed arguments. We were also interested in examining which argument components were important for the quality of arguments generated by these students. Two hundred and ninety six writing samples were scored using an analysis framework to evaluate the quality of arguments. Step-wise multiple regression analyses were conducted to determine important argument components. The results of this study suggest that the SWH approach is useful in assisting students to develop reasonable arguments. The critical element determining the quality of the arguments is the relationship between the student's written claims and his or her evidence.