Research evidence suggests that appropriate use of formative assessment promotes effective learning. Improved learning occurs when assessment is viewed as integral to learning and is situated throughout a student's school experiences. This extends beyond the more formal assessment tasks that students experience and includes a wide range of less formal activities and interactions that occur as part of the day to day classroom. One of the key pedagogical techniques available to the teacher to promote formative interactions is effective questioning. However, not all questions asked by teachers are used for formative purposes. At times this is due to design of the question. At other times it is because potentially useful information was either not recognised by the teacher, or not followed up on. This presentation draws on data from the LPS Project in New Zealand to investigate effective questioning in secondary school mathematics classes. In particular, it examines the characteristics of questions that encourage ongoing dialogue within a community of learners in order to guide students learning effectively. In examining this issue, this paper adopts a contemporary socio-cultural perspectives of learning that recognise the situated nature of knowledge, and the impact of the social environment in promoting and directing learning.