This study investigates children's changing sensitivity to processing cues for identifying agent (word order, case marking, and animacy) as a function of proficiency in a second language. English-speaking learners of Japanese need to appropriately adjust cue strengths in moving from a rigid SVO language to one in which SOV word order is a good general processing strategy, but case marking must ultimately be relied on if it conflicts with this order. English-speaking children in grades K–7 in an immersion school were asked to identify the agent for a set of audiotaped sentences in English and Japanese. The children in this study learned to use SOV word order, lexical semantics, and canonical case marking, but they do not provide evidence of appropriately exploiting noncanonical case marking. We suggest that these results might be accounted for by the context in which input is processed in immersion school classrooms.