LaMelo Ball Throws Down Nasty Windmill Dunk, Disses His Old High School

Looks like LaVar's homeschooling is already paying off -- 'cause LaMelo Ball is suddenly crammin' home windmill dunks!!

And throwin' shade at his former high school -- saying they're gonna suck now that he's gone.

In the video, young Melo grabs the rock off a bounce and throws it down ... before turning up with his boys at a pickup basketball sesh.

The youngest Ball bro hasn't been filmed getting up like this before, so you can see why they're all so pumped.

But arguably the best part of the vid comes at the end ... when LB slams Chino Hills, saying -- "Mark my words: Without Melo, they losing."

Guess LaVar's not the only one excited with the move.