There has been a huge and unparalleled increase in the numbers of paraprofessionals working in schools, particularly classroom-or pupil-based support staff, referred to throughout this book as ‘teaching assistants’ (TAs). This book provides the most comprehensive picture of the consequences of this change for schools, teachers, pupils and the TAs themselves. We start with a vignette that provides most of the essential results from the Deployment and Impact of Support Staff (DISS) project and reveals the key themes we will be addressing in this book. It provides a description of one small extract of classroom interaction between a teaching assistant and a pupil. We then put this into context by drawing on further information on the classroom interactions and behaviours at this moment in time, the TA’s activities over the school day, and then information from the TA, the class teacher, the headteacher and the general context provided by government. In this way the small piece of classroom interaction between a TA and a pupil is nested in progressively wider sources of information and influence. Finally, we provide information on the relationship between the amount of support the child receives from a TA and the pupils’ attitudes to learning (e.g. independence and motivation), and their academic progress. All the information provided is real and comes from – and is representative of – data collected as part of the DISS project, though the names and some minor details have been adapted. The vignette describes the situation in a primary school but most of the details, with some differences concerning the deployment of TAs, which we will describe in this book, also apply to the situation in secondary schools.