I think the five most important events leading up to the climax are:
1. Archie gives Jerry an assignment to refuse to sell chocolates for 10 days, and then agree to sell on the 11th day.
2. Jerry decides not to ever sell chocolates, and his defiance spreads across the school.
3. At the Vigils' request, Jerry is harassed by getting prank phone calls, the football team refuses to catch Jerry's passes, and Janza beats Jerry up with a few of his friends.
4. The Vigils manipulate the chocolate sale so that all but 50 boxes (belonging to Jerry) are sold.
5. Archie sets up the fight between Janza and Jerry in the school assembly, pretending that the 50 boxes of chocolates will be raffled off.