Dave standing up to Mr. Neck's xenophobic remarks.
The turkey-bone sculpture, with a duct-taped Barbie head and the bones shaped into a tree sculpture. Mainly because Mr. Freeman and Ivy intuit the emotions presented within the piece.
Melinda refusing to help Heather after the former has dropped her in favor of more "popular" friends. Becomes a "Reason You Suck" Speech in the film.
Though it earns her a D on her assignment, Melinda finding a loophole to giving an oral report, and Dave helps. They pass out copies of her report to the whole class and plan to have her stand for the required duration of her presentation.
Melinda playing tennis, and winning a match against the class athlete.
Melinda standing up to Andy in the climax and actually scaring him. "I said no."