The rubber band ball is very useful in the Smash It Up mission. Go to the warehouse with Zoe and begin the mission by throwing a couple at ground level. Then, climb high and begin launching the rubber band balls everywhere. If done correctly, should complete the mission on your first attempt.
1. Autoshop roof. 2. In the "Help Gary" mission, on a table in the boiler room. 3. Behind the Mexican restaurant in Bullworth. 4. In the fourth photography class on the Bullworth dam. 5. In the "Nerd Challenge", on the table next to the stairs. 6. Found on the ground just before you enter "The Tenements" building.
Violating your curfew isn't necessary to unlock the achievement. Just go inside the boys dorm when it is 11 o'clock. Once in the dorm, pause game play. Go to the time spent out after curfew and it will still count as time out after curfew.
To unlock the "Kickin' The Balls" achievement you have to kick a soccer ball 100 times. Use the soccer ball located outside and to the right of the Boys Dorm. Go to the right-hand side of the dorm and keep kicking the ball against the wall. If you wait until after 11 p.m. to do this, you can unlock the "Kickin' The Balls" and "After Hours" achievements in just two nights.
Climb up the ladder and position yourself facing the direction of the other roof where you see the rubber band. Press LB or RB to skateboard, then press the Left Analog-stick Up + B to jump to the other roof top. Immediately press LB or RB as to not roll off the roof.