Basically, Urie Bronfenbrenner ecological theory of development is based on a nested model (kind of like those Russian nesting dolls). At the core of the nested model is the individual. Each layer within the nested is interdependent and intradependent of each other, which means that each layer affects one another. The layers imply the services and needs the individual (at the core) needs to have a balanced life in society, and they include school, social services, family, religious groups and, in general, every community resource available.
The premise of the theory is that we are dependent on the proper provision of the services and resources available in the community. If each system on its own is operating properly, then the chances of the individual will get the best care conducive to the best development possible. This is basically why the individual is nested right in the center of the model, and each layer influences greatly the path towards a good citizenship.