A 6-year-old girl is referred by her school for not speaking in the classroom despite being enrolled for 5 months. Her teacher reports she has never spoken a single word at school, does not respond verbally to peers or teachers, but follows instructions nonverbally and participates in written activities. Her parents report she speaks fluently and age-appropriately at home with family members, engages in imaginative play, and demonstrates normal social reciprocity with her siblings. Developmental history is unremarkable with no speech or language delays.