MIT (Studious) Model
The MIT model of Physics education involves creating strong student groups that explore Physics. The actual teaching takes place not in the lecture hall, but late at night in a dorm room around a problem set that will be hand graded. The problem set does not produce a large proportion of the grade, and consists of very difficult problems, making it generally impossible for individuals to complete them on their own.
Many things subtly contribute to make this approach effective. Even though it is theoretically possible for students to simply copy the answers and hand them in, it is not in their interests to do so, because they would fail the test and final examinations, which form most of the grade. Moreover, it is to the students' benefit to know what their weaknesses are because they get very detailed feedback in the problem sets.
The other important aspect is that the passing grade is set extremely high, and the grades are against some more or less objective standard. Because the pass rate is very high, there is no disincentive to helping someone else learn the material.
Additionally, tests and finals are hand-graded, with the possibility for generous partial credit. The emphasis is placed on the concept, and not on just getting the answers.