Oi, How do you even get 100%?
I've done all the story and optional mission, collectibles, etc, But I've only got about 80%.
..
Anyway, I never go to classes once I've completed them.
Aside from that, Jimmy's only ever missed ones early in the game when I was still figuring what I was supposed to do.
And later when I knew what, and whose classes I should avoid.
Mainly the ones that give lame prizes.
Rubber Bands
G&G Cards
Gnomes
Complete all 14 Bike Races
Complete at least 30 errands
Complete all 6 levels of Lawn Mowing
Complete all Paper Route levels
Side task Boxing
Ride all 3 Carnival rides
Win at all 4 Carnival games at least once
Beat Penalty Shots once
Beat Keep Ups once
Complete all 5 levels of all classes
Get high score in Consumo, Nut Shots and Monkey Fling arcade games
Buy all clothing in the game
Buy 100 sodas
Smash all Pumpkins from Halloween
Smash all Tombstones from Halloween
Pull 20 fire alarms
Travel 100 km on a bike
RUN at least 41.8 km
Fail any three classes
Take all Yearbook photos
Win at least the first Go Kart race
Beat up the hidden secret pirate
Here's the checklist. If you have done all of this, then I don't really know how to achieve 100%.