Visually speaking, the film is spectacular. It's like Tim Burton in pastels. Beautiful, creepy, girly and gothic. If I were basing this off aesthetics alone, I'd rate it five stars.
But the storyline is... Well, "Cats: the Musical" has more of a plot than "K-12" did. I can tell you things that happened in the movie but I can't tell you what it was actually about. A lot of details or subplots are touched upon and then entirely discarded, some scenes feel out of context, quite a few of the songs feel forced into the story, none of the characters show any real depth or development.
I think what happened is Melanie was overly ambitious and overestimated what she could reasonably manage with 90mins and whatever budget she had. She wanted to touch on a lot of important societal issues, which I respect, but in order to fit so many, they were only briefly discussed, added nothing to the story, and were then discarded, which made the impact of it very minimal.
A lot of the dialogue was fairly cliche and I didn't find the acting to be overly believable at times. It often was just your basic conversation between friends at school, which I guess makes sense given the school theme, but it often added little to "story", which probably contributes to how it felt like there was no actual story.
At one point, a character said something like, "Even I'm not flaking for once," and I wondered what the hell she was talking about because she literally just became a character and had said like five words before that. I think it was around "Teacher's Pet" that I realized I was reaching the end of the album and still had no real idea what was going on.
I had questions. So many questions. Too many questions. I get leaving some questions so that the viewer is interested in a sequel, but I felt like literally none of the questions brought up by the movie ever got a satisfying answer.
I love the album, though. Every song is pretty much stuck in my head. Watching the movie was worth it for hearing "Fire Drill" alone, since it's not on the album proper for some ungodly reason. She better actually release it as a single or deluxe track or something, though, because I like it more than at least half the songs on the album.