Ever wondered why we encourage children to work for stickers? Urge them to display acceptable behaviour for extra golden time? Or show caring and supportive attitudes for certificates?
B. F Skinner developed the system of "token economy," originally designed for use in prisons and mental institutes. The inmates were required to display appropriate behaviours and complete necessary chores, in return they would receive tokens that could be traded in for luxury items, such as cigerettes or playing cards.
The psychology of behaviour is fascinating stuff and a brilliant way to understand the behaviour, of not only your SEN children but all children.