First-year classes are difficult. After that, though, there is no core: you really only need to fulfill a couple of requirements to graduate (substantive writing projects, a professional skills course, a class on legal ethics). Even those are categorical, though; there's no requirement to take a particular class.
Seminars are by and large great. Who is teaching and that person's teaching style can have a huge impact on whether a class is a total dud, though.