Kant identified that source as morality. Habermas objects that morality is tied to specific religious and spiritual beliefs that in the age of phenomenology are subject to question. Habermas objects that the ethics approach is no longer feasible in the face of global pluralism. He suggests that the legitimacy we tend to see in natural law must come in the twenty-first century through democratic discourse and agreement on those values in which we can all believe. Habermas also insists that we must all participate in such democracy.
Exclusion confounds the legitimacy.
This is the point at which our experience fails us, and rightly so. When the test is a basic writing, or basic math test, there has been some general institutional agreement that passing that test indicates a fundamental standard. Yet the institution views the test as a neutral test, required for all. Logic dictates that there may be a minimal standard set for all, especially when a society is concerned with raising educational standards. The student's objection seems to attempt the social reconstruction of logic, that somehow lower standards for some people, or groups of people, will not lower overall standards for the whole society.