A student who is new to the United States understands some English, but his vocabulary is limited, and his grasp of syntax is weak. Although he is 11, his previous education was very limited, so he has been placed in a 4th grade classroom. For the first few weeks, he was very quiet and kept to himself. In an effort to bring him out of his shell, his teacher put him into a pod with several highly social students whose first language is English. The students tried to draw him in, talking loudly and gesturing to make him understand. When he ignored them, they left him alone. To her dismay, the teacher's previously quiet student grew sullen and very angry. He hit a child during recess one day and stormed out of class in the middle of a lesson the next day. What is most likely the problem with the boy?