When a high school kid tricks out his inadequate car (usually a cheap Asian import but is not limited to crappy domestic and European cars) to make it look and sound like it is fast when really it’s slow and sounds like a lawn mower on steroids. This is often done because they cannot obtain a real performance car because of the lack of funds. High schooling out includes a big oversized spoiler, large exhaust pipes, stupid performance stickers, and a John Deere intake kit for that high performance lawnmower sound.
"Hey, did you guys check out Timmy's wheels?" "Yes, its really high schooled out!"