Children living with visual impairments (VIs) are increasingly educated in mainstream rather than special schools. But knowledge about the challenges they face in inclusive schooling environments and how to design technology to overcome them remains scarce. We report findings from a field study involving interviews and observations of educators and children with/without VIs in mainstream schools, in which we identified the "teaching assistant bubble" as a potential barrier to group learning, social play and independent mobility. We present co-design activities blending elements of future workshops, multisensory crafting, fictional inquiry and bodystorming, demonstrating that children with and without VIs can jointly lead design processes and explore design spaces reflective of mixed visual abilities and shared experiences. We extend previous research by characterising challenges and opportunities for improving inclusive education of children with VIs in mainstream schools, in terms of balancing assistance and independence, and reflect on the process and outcomes of co-designing with mixed-ability groups in this context.