Just as paediatricians are the gatekeepers to children’s physical health, preschool teachers are the gatekeepers to children's overall developmental progress. Their perceptions shape their interactions with their students and guide referral for special education. The implications for students’ academic/developmental trajectories are manifold, requiring accuracy and sensitivity. This study compares teacher-reported subjective scales of development and expressive language ability to student performance on objective measures in these domains, and asks: (1) Are preschool teachers accurate in their perceptions of student overall development and expressive language ability? (2) Are teacher perceptions of expressive language ability more predictive of overall development than expressive language scores as measured by an objective assessment? (3) What implications does this have for teacher intervention and referral? (author abstract)