A few things that IMO would make a difference:
1) The profs themselves must edit Wikipedia (preferably having brought something to GA or FA within their subject area). And if we are going to go with large classes than so must their teaching assistants. The only way to learn how Wikipedia works is by editing content.
2) There must be a number of hours of in class instruction on Wikipedia's policies and procedures. One does not begin writing for the New England Journal of Medicine without first learning their manual of style and referencing requirements.
3) If classes are working on content they should concentrate on improving the quality of one or a few articles. Assignments such as "go out and make an edit to the subject area of this class" should not be repeated.