Brooklyn Nets star Allen Crabbe tells TMZ Sports ... cutting a 6-figure check to save an L.A. school was a "no-brainer" -- because giving back to the community is more important than ballin' out.
We broke the story ... Crabbe stepped in with a "miracle" donation to Frederick K.C. Price III Christian School in south Los Angeles last month ... saving it from closing permanently.
Crabbe went to school there -- and has several members who still attend -- and felt a moral obligation to help out when it couldn't afford to pay the bills.
"My mom texted me saying, 'Look, nobody has come forward with a donation, can you give this amount?' And I was like, 'Yeah, I'll do it!'"
Crabbe -- who's in the middle of a 4-year, nearly $75 million contract -- says he's blessed to be making such a high salary and says he wants to use that money to give other kids a chance.
You gotta watch the clip ... Crabbe's as humble as they come.