If your school has a ground school and it works for with your schedule than I think it is a valuable tool in learning the required items. It is a great way to meet other student pilots and can be a support group for you.
DVD courses can include so much, and I feel personally that they are a great way to learn. For me going to a ground school was difficult, I had a job for every license/rating past my private license and did home study courses (there were no DVD courses wayyyy back then).
When I was introduced to DVD courses at a school I was an instructor at, it made me a believer. Along with a syllabus the student and instructor are all on the same page. You see the flight manuevers before you do them and so much of the mystery is gone and true learning can begin.
The ideal situation is to do both, it depends on your learning style, the type of school you are going to and your schedule. This subject is a very good one to start with as you interview schools/instructors.