Gwyneth Paltrow -- A-HOLE DRIVER OF THE YEAR ... Cuts Off School Bus On Vespa

Gwyneth Paltrow might be the worst driver in all of Los Angeles (and that's saying a lot) 'cause she CUT OFF A SCHOOL BUS ON HER VESPA WITH HER KID ON THE BACKSEAT ... and it was all caught on tape.

Paltrow and husband Chris Martin were picking up their kids from an L.A. school last week on their respective Vespas ... when Paltrow (with one of her young kids on the back of her scooter) darted out into traffic ... right in front of an oncoming school bus.

The bus driver had to slam on the brakes to stop from plowing into the actress ... and GP scooted away as if she didn't just put a bunch of people's lives in danger.

FYI -- school buses are giant and yellow and generally pretty hard to miss ... so we can't really understand why Gwyneth didn't just wait the 2 minutes for traffic to slow down before leaving the school.

We called Gwyneth for comment -- so far, no word back.