A coherent and consistent approach to K-12 science education depends on having high-quality assessments of students learning. However, designing assessment tasks based on disciplinary core ideas, science and engineering practices, and crosscutting concepts to align with intent of the Framework for K- 12 Science Education (2012) and the Next Generation of Science Standards (NGSS; 2013) is challenge. The purpose of this study is to show the process of developing the assessments tasks that aligned with NGSS performance expectations using principles of evidence-centered design (ECD). We mainly focused on the first two steps of ECD to develop design patterns and task templates: (1) unpacking performance expectations (PEs) and (2) specifying instructional level performance expectations (ILPE). In unpacking, we identified target PEs for assessment tasks by clustering related PEs in a topic, elaborated on science ideas and boundary conditions, and explicated necessary prior knowledge and common challenges. To specify ILPE, we considered the relationships between the claims to be made about what students know and can do, the evidence that would demonstrate competency with respect to these claims, and the features of tasks to elicit the desired evidence of the specific PEs. Our work shows that applying the ECD design pattern is an effective process for developing assessment tasks aligned with PEs in NGSS. The unpacking step helps developers to clearly understand PEs in all three dimensions. The specifying of ILPE step helps developers identify tasks which align with PEs that demonstrate evidence of student learning. Our next steps involve empirical studies to determine if the assessment tasks provide the expected evidence of student learning.