if you look at the site that was given in post #5, assuming you know which classes you intend to take (need to research some), that should give you a rough idea of how easy or difficult a class is. Any classes where the average is some sort of A will probably be easy. B+ are not too bad, but still difficult. B are the hard classes, and B- are really difficult and hard classes. There are no classes that average below B-.
History 7A is B+
History 4A is B+
as examples.