As new science standards increase emphasis on the teaching of science and engineering practices, research is needed on the implementation and outcomes of students' experiences with authentic inquiry-based activities. Using a framework on teacher support for inquiry, we examined results from a national survey of middle school science fairs. Three types of science fairs emerged: those that were mandatory with high teacher support, those that were mandatory with low teacher support, and those that were voluntary. Mandatory fairs with limited teacher support were more common in schools with a high proportion of African American students and high poverty, but were more likely to focus on the learning of content and practices.