The fundamental difference between a Sudbury school and any other type of school is the student's level of responsibility. In a Sudbury school the students are solely responsible for their education, their learning methods, their evaluation and their environment.
In a public school, the state takes responsibility for most aspects of a student's education including curriculum and evaluation. The student is left with little responsibility except to learn what is taught, how it is taught, in the environment in which it is taught and then to reiterate it back at evaluation time.
In a non-Sudbury private school, the school administrators take a larger role in determining a student's curriculum than in a public school. In some private schools, the school takes responsibility for evaluation, while in others the school administers the state tests. In most private schools, as with public schools, a student has personal responsibility only for learning what someone else determines is important to learn, at a time they think it is important to learn it, in a way someone else has determined it should be taught, in an environment designed by someone else, and they must do this well enough to pass the evaluations written and graded by someone else.