This chapter provides the young language learners' characteristics in relation to the development and use of English language proficiency (ELP) assessments. It describes a few key aspects to consider in the development and use of standardized ELP assessments given young learners' characteristics. The chapter focuses on a new assessment design technique called "scenario-based assessment (SBA)" and illustrates how technology-enhanced SBA can be used in standardized assessment settings as well as formative assessment settings to support young learners' reading assessment and development. It offers a unique perspective on the assessment of young learners and provides stimulating ideas for conducting future research and development work to improve ELP assessment practices with young learners. Standardized ELP assessments for young learners can provide information about individual students' achievements and levels of proficiency based on international, national, or local standards/curricula and individual students' growth in their ELP attainment.