This one can be rather slow to do since you cannot egg the same car over and over for this one.
You'll have to wait until Chapter 2 onwards to attempt this also since there are no cars to egg in Chapter 1 within the School grounds.
It is best to wait until you can buy eggs from the shop or better yet, wait until the eggs respawn in your dorm room in front of the Chemistry set.
A car almost always spawns outside Bullworth Academy when you leave the gates so just make it a habit to have eggs on you and when you see a car on your travels, block its path (it will stop still), equip your eggs and hit the car with the egg (Press up on the d pad to use free aim).
Be sure to run after you egg each car because the grown up driving will chase you everytime and will attempt to bust you, they are easy to outrun though.