The first season had a strong coherent story that, while not perfect, had it's merits and knew what it wanted to accomplish.

After that it becomes a mostly lame teen drama with a lot of inconsistent messages and cliche elements. The quality of the show flips from mostly solid with some subpar to mostly subpar with some solid after season one ends.

Most of the cast is capable. The writing is what keeps it from being in a better echelon of shows. It really feels like they had a contained story...saw it was a hit then decided to keep it going when it was actually unnecessary.