Across the curriculum, the questions that teachers ask in class direct learners' attention to key subject matter, and shape what they learn. This paper examines the types of questions that Chinese school Biology teachers ask, and considers how and why they vary their questioning in the context of scientific practices. Six teachers from four schools in Xi'an City in mainland China took part. Three lessons were observed for each teacher, followed by interviews in which teachers were asked to focus on specific teaching episodes and explain their questioning. Findings reveal that teachers' questions were mostly closed-ended, but in certain types of lessons their questions were more open and they used questions to manage class discussion. Teacher questioning is affected by personal beliefs, institutional working practices, and external policy shift, and teachers experienced tension in navigating between these factors. The results have important implications for policy and practice; for example, teacher educators need to recognize the complexity of teacher questioning and encourage teachers to discuss the challenges associated with asking more open questions, while policy-makers need to acknowledge the impact their decisions can have at the classroom level.