Lap?

It just seems like an error. Where did you find this sentence?

messier42My little brother is about to lap him at graduation.

The only meaning that remotely makes sense to me is "overtake someone on a circuit" (e.g. a running track or racecourse). I suppose this could be stretched to mean "greatly surpass". This idea could be completely wrong though.

I'd make it to school before 7:30 AM, either by school bus or my mother's Taurus, and then wait out options for escape. By my sophomore year, this kid named Tony Garcia had become my primary friend. Tony was nearly 19 and only a junior, but he didn't seem all that bad because he had good parents and an even better little brother, who was about to lap him at graduation.

My guess is the meaning is this.
Tony's little brother is about to graduate a year ahead of Tony.

But it's an odd and unclear expression.

CliveMy guess is the meaning is this.Tony's little brother is about to graduate a year ahead of Tony.

I think you're probably right.