With very few exceptions, it’s preferable to offer service learning as an option. Most students don’t know they’re in a service learning course until they walk into class the first day. To spring service learning on them and then require it may lead students to drop the course or do the service with a less-than-cheerful heart. If your course is one in which community service is an integral, logical element (such as Dorothy Day and the Catholic Worker Movement), you may be able to convince students that a mandatory community experience makes sense.
There is a school of thought that says service learning should be viewed like any other course requirement, i.e. you wouldn't offer students the option of taking exams or writing papers, so why offer optional community service? While this argument has merit, the difference is that you may be asking students to do things that make them very uncomfortable (e.g. ride a city bus to unfamiliar neighborhoods, provide direct service to a population with whom they’ve had little or no prior contact, etc.). Requiring such an experience without informed consent doesn't seem wise.
However, in classes using models other than Placement (Product, Presentation, Project), where students are in groups and do most of their work on campus, we see no problem with requiring service learning.
Some of our professors offer a nice middle ground approach: They tell their students that doing service learning is the “norm” for their classes. Choosing the traditional option (research paper) is the exception.
