thousands of pupils have already been sent home after positive cases. And while in some schools, like Green End Primary in Burnage, a positive case has affected just one class of around 30 children, in others, hundreds have been sent home to self-isolate.The government guidance is to keep bubbles as small as possible - 'if that can be achieved' - to limit the impact of a positive case on the school community.But it admits that in secondary schools, particularly in the older years, groups are 'likely to need to be the size of a year group to enable schools to deliver the full range of curriculum subjects and students to receive specialist teaching'.Despite the obvious preference for smaller bubbles, schools have been facing their own.