Message to aspiring screenwriters: You do not need to give your script a "message." Movies don't have to be learning experiences. It can work out that way in the end, but if you're trying to sell us medicine, the sugarcoating had better well be worth it.

Not to sound cutesy, but "Charlie Bartlett" isn't that sweet. This unwieldy mix of "Rushmore," "Ferris Bueller's Day Off" and the 1990 Christian Slater classic "Pump Up the Volume" has a lot of promise that it ultimately squanders.

For about an hour or so, I really enjoyed this flick. Granted, you have to get past the premise, wherein the title character (Anton Yelchin) rises to fame and popularity in his high school by acting as de facto psychiatrist and prescribing prescription drugs to the student body. To call this "irresponsible" is an understatement.

Yet the flick still works for a time. It's an unusual kind of comedy; it doesn't go for big laughs. It's genial rather than uproarious, pleasant rather than hilarious. I smiled far more than I laughed, and I think that's the flick's intention. There's a laid-back, understated air to the whole thing — it gets more juice from quiet observation and performance. I was reminded of director Bill Forsyth's sly, gentle comedies "Gregory's Girl" and "Local Hero." This helps the flick. Bartlett approaches his new "responsibilities" with quiet amusement, and the flick seems far less unsavory as a result.

This hour isn't perfect. I had some quibbles here and there, like how Charlie Bartlett can succeed academically without really spending any time in a classroom, or how the Connecticut of the flick seems suspiciously like the suburbs of Toronto, but if you move past stuff like that, you'll be fine.

There are so many pleasures to be found here, from the sly, knowing mother-and-son relationship Charlie and his mother (Hope Davis) share to Charlie's genuine and boundless optimism in the face of all opposition (most notably in his handling of a local bully, which starts out adversarial and slowly grows into something far more special).

If the flick had followed this pleasant, aimless path to the end, it could've been really special. And then, at the hour mark, it self-destructs.

Spectacularly.

The second we get a "Rules of Attraction"-esque suicide attempt, the flick falls apart. The movie becomes rushed, throwing in all sorts of tedious and predictable plot points; the sitcom elements (resolutions of all major issues, unrealistic character shifts) grow more pronounced; and worst of all, it goes all after-school special on us, turning into an indictment of medicated behavior/culture.

In its biggest offense, the last 20 minutes are pretty much deadly serious as we focus on some major and jarring insecurity on Charlie's part and a half-assed study of the horrors of alcoholism. It's heavy stuff, and the flick just cannot support that weight. It's just too unsubstantial to do so.

I just don't see why writer Gustin Nash and director Jon Poll let the flick go like they did. The end is just sloppy writing, plain and simple, as Nash tries to bridge the humor of the first hour with his ham-handed messages. News flash: the Hays Production Code is no longer in force. Bad behavior in movies doesn't automatically have to be punished anymore.

Maybe the tonal shifts would've seemed less distracting if Poll were a better director; he handles them with no grace, no logic, and I kept wondering what a Jason Reitman or a Judd Apatow would have been able to mine from this script.

What does work, even when the flick around them is flailing, is the actors. Yelchin's Charlie Bartlett may be just an amalgamation of Max Fischer and Ferris Bueller, but he brings a real innocence and guile to the part and makes it his own. He also a has a nice, unforced chemistry with his on-screen love interest, played by Kat Dennings, who comes off like a much funnier and far more self-aware Scarlett Johansson. As Bartlett's mother, Davis is really amusing, a kind of over-medicated Morticia Addams, but she's hindered terribly by a horrible post-prison scene where she beats herself up as a mother.

And then there's the only flawless part of the flick: Mr. Robert Downey Jr. As school principal Gardiner and main adversary to Charlie Bartlett, Downey's got an impossible character to play; the script can't decide if he's the comic relief or the villain, and it would probably be painful to watch a lesser actor try to feel this guy out.

In response, Downey does something surprising and kind of wonderful — he turns Principal Gardiner into a tragic figure, an alcoholic, deeply sad man still struggling with all the inadequacy and self-resentment stored up from his own high-school days. Downey not only overcomes the scripting violence done to him by Nash, but he also becomes the most interesting and compelling character in the flick. This is lovely work, and a further reminder that, along with Daniel Day-Lewis, Downey may be the finest actor working in movies today. "Iron Man" can't come soon enough, I tell you.

The fact that I was enjoying "Charlie Bartlett" so much early on makes it that much more disappointing. It's not content to just be pleasant, so it tries to be everything, and ends up failing at most. It's rare that you'd want a movie to underachieve, but I guess there's a first time for everything.