I used to be in the top ten, but got bumped out! High scores depend a lot on your teammates, since your points-per-fix increase with each level, and you can only advance to further levels if everyone is working quickly. If you have three CPU teammates, your score will be limited.
Here's a tip: when you're about to power up and advance to the next level, pick up a color that's not yours, but for one of your slower teammates.