Usually it is easier to produce systems change through advocacy with a group that has related advocacy goals. It is easier to destabilize a weak constraint in the system if there are several similar but somewhat different ways for the system to lose control of the destabilized constraint. A standard model of this process might involve eliminating a segregated classroom by arguing that each student in the class has a right to an integrated educational experience and doing this through a group collaboration.
Each student can pursue a separate action to move to an inclusive environment, since the typical reason why a system would segregate a group of students is to reduce the costs of similar supports for these different students. If the system loses even one of these advocacy initiatives, they will have to provide the supports outside the cheap classroom, and they will have to absorb the cost of the hearings that advocacy triggers. So, 6 students can mean 6 hearings, six separate hearing costs (maybe $20,000 each). It is cheaper in the long run to develop a model that provides the supports that would be ordered in a hearing result.
Also, systems have developed methods to isolate single family advocacy efforts by demeaning their competence, educational knowledge, purposes, impact on other students, and so on. These tools are far less usable when there is a group of similar advocacy efforts.
A group with a common purpose forms a temporary complex adaptive system (CAS). This purpose is the governing constraint and frames a set of possibilities that the group will explore as it moves toward a valued outcome in their work.
In addition, a group with a purpose can more easily pursue destabilization of many additional weak constraints that are part of the system. Political activities, public relations, educational initiatives, public policy planning, and many other possibilities for advocacy are much more feasible in a group.