This chapter discusses the challenges of both developing assessments for young learners and building validity arguments for test development and score use, focusing on large-scale standardized tests such as the TOEFL Junior tests, the TOEFL Primary tests, and US K-12 English language proficiency assessments developed by Educational Testing Service (ETS). It discusses how the contextual and theoretical changes create new challenges for developing and validating assessments for young learners, particularly standardized tests. The chapter describes Kane's and Chapelle et al'.s interpretative arguments, and discusses current challenges that face in validating standardized English language proficiency (ELP) assessments for young learners. The argument-based approach, at least the validity inferences that have been identified, does not seem to provide researchers with an appropriate framework for learning-oriented assessment. The chapter needs a clear conceptualization of the role of learning in standardized testing.