Charlie Bartlett (ANTON YELCHIN) is a 17-year-old with a penchant for concocting such outrageous schemes that he's just been kicked out of the last private school in the area. With his dad gone and his mom, Marilyn (HOPE DAVIS), not exactly the best role model around, Charlie copes with his feelings of not fitting in by trying to befriend everyone.
That's a good tactic, because things don't initially appear promising at Western Summit High School, a public institution run by Principal Gardner (ROBERT DOWNEY JR.) where bullies such as Murphey Bivens (TYLER HILTON) don't think highly of preppy kids such as Charlie, and thus beat him up.
In fact, everyone is aghast when Charlie sits with mentally challenged student Len Arbuckle (DYLAN TAYLOR) at lunch. Yet, Charlie has ulterior motives as he then uses the hulking kid to put Murphey is his place, and then proposes a business arrangement with the bully. Since Charlie is already seeing a number of psychiatrists, and realizes his classmates aren't getting the help they need, he proposes that he and Murphey sell the other teens various forms of prescription medication.
Setting up office in the school bathroom, Murphey dispenses the drugs and Charlie the advice, soon drawing the likes of promiscuous cheerleader Whitney (MEGAN PARK), depressed kid Kip (MARK RENDALL), and even Principal Gardner's daughter, Susan (KAT DENNINGS), as paying customers. When his popularity suddenly increases and he starts dating Susan, Charlie draws her alcoholic dad's attention, thus leading to a number of confrontations between the two, with the student body standing firmly behind their new prescription and psychology guru.