This article explores the pivotal role of rumour in shaping primary school choice decisions for parents of children diagnosed with autism. Drawing on semi-structured interviews with 22 mothers conducted in Sydney, Australia, this study points to the varied functions of grapevine knowledge about schools gleaned in diverse contexts, including early intervention settings, support groups and neighbourhood communities. Parents, especially mothers, provide one another with pragmatic information about schools as well as advice on how the education "system" works. They also repeat "horror" stories of bullying incidents and social exclusion that have a powerful affective force. Educational sociologists have referred to this as "hot" knowledge. These data demonstrate the need for more detailed analyses of hot knowledge in understanding how families of children diagnosed with autism make choices between segregated and mainstream education options, as well as deciding on particular schools or classrooms within the various sectors of the education market. In studying these processes, we gain a better understanding of how mothers negotiate multiple forms of knowledge during periods of school transition and of the importance of this process in forging maternal identity. The qualitative research presented helps us to conceptualise broader processes of social inclusion and exclusion experienced by these families.