Just as no two people are alike, no two organizations are alike either. Some organize along traditional lines with clear ranks and responsibilities, while others seek to remove these layers to improve communication and collaboration. There's no "one size fits all" for public sector agencies either, although most are organized hierarchically around vertical chains of command.
In the United States, the public sector comprises federal, state and local governments including bodies like homeland security, taxation agencies, the military, the Department of Health, public schools and corrections. The United States Postal Service is considered part of the public sector although technically it's an independent agency with revenue-generating goals.
The private sector comprises everyone else – businesses that are privately owned and not controlled by the government. These organizations tend to have much more flexibility in the way they are structured. For example, a small business might have an extremely loose structure when it first starts out, with people taking on multiple roles and job functions. The business is then free to add positions, managers, product groups and layers of responsibility as it grows.
Government agencies have far less freedom to add new functions, services or job positions. That's because these entities are created by legislation, which often specifies how the entity should be constituted and what it has to do in order to change leadership teams or get a new job position approved. They are also built on legacy, having developed their organizational structure over many years.
The structure of the public sector is best described as a hierarchy. This type of structure resembles a pyramid and gets wider as you move down. This type of organization, whether public or private, is headed by a board of directors, a board of trustees or even a single director who could be an elected official. Below that are multiple layers of management – senior managers, middle managers and line managers – with instructions flowing downward and accountability flowing upward vertically through the chain.
Roles are clearly defined within this structure, and everyone knows to whom they should report, which helps the agency be accountable for its decision making. This structure also allows people to focus on their area of specialty, as people with certain job functions are grouped together with other people who share the same area of expertise.
On the downside, horizontal communication between different divisions may be poor, as the system is built around a vertical chain of command. All these layers of bureaucracy can slow down decision making and create departmental silos that make it difficult for the agency to collaborate and adapt to change.
To see the public sector approach in action, look no further than the military. In the United States, all branches of the military use a fixed rank structure where each person's rank determines his position in the hierarchy. There's a very clear top-down chain of command, with each rank being subordinate to the rank above and superior to the rank below.
If you look at other public sector organizations, you can see that they are modeled on the military system. Police departments, for example, are usually headed up by a chief of police. Below that, information and responsibility is passed down to a lieutenant and then to sergeants who supervise various units such as patrol, investigation and call dispatch. Rank-and-file police officers sit at the bottom of the pyramid, allowing work to spread evenly across the department.
On the face of it, a public school or university might look very different from a police department, but the organization is roughly the same. Again, you have a person at the top – the principal – who is supported by a vice principal and administrative staff. Below that you have faculty heads, tenured teaching staff, teachers of varying seniority and teaching aides. The leadership team calls the shots on strategy and creates the conditions that encourage great teaching on the ground.