LeBron James traded in his signature Nike kicks for a polo and clipboard on Wednesday, coaching up son Bryce James at one of the most heralded H.S. hoops tourneys in the world!

It all went down Wednesday afternoon at Nike's Peach Jam in North Augusta, SC ... which features some of the best high school players from around the country, competing against each other.

16-year-old Bryce hoops for SVG -- Strive For Greatness -- and while LeBron isn't technically the head coach, he shared some of his wisdom with the squad as they took on the Florida Rebels.

And, the King wasn't alone ... 2x NBA champ Rajon Rondo was also there, assisting.

FYI, Bron and Rondo aren't the only big names around ... Chris Paul, Bradley Beal, Carmelo Anthony, and several other NBA stars also have teams.

Rivals reporter Krysten Peek even captured video of Bron drawing up a play during a timeout, while the former Celtics star coached up one of their players on the side.

SVG won their first game on Monday ... where 6'4" Bryce, who recently transferred to Campbell Hall from Sierra Canyon, dropped 12 points (on 4-of-9 shooting).