7:39 AM PT -- Meek surprised hundreds of kids when he showed up at his alma mater, James G. Blaine Elementary School, Wednesday morning to donate some backpacks.

Philly better not boo this Santa ... Meek Mill's doing right by the city of Brotherly Love and spreading cheer early to a bunch of kids just in time for back to school.

Meek Mill's teaming up with Puma, sports apparel Fanatics, United Legwear and Philly's luxury store Milano Di Rogue to donate more than 6,000 backpacks to students in the city.

We're told there will be 3 types of backpacks -- for elementary school, middle school and high school students. The kiddos get pencil sharpeners, rulers, glue sticks and crayons -- while it's dry erase markers, notebooks and pens for high schoolers.

Meek tells TMZ he knows firsthand what it's like for families to struggle financially around back-to-school time. He says, "Those memories stay with me and that’s why I’m committed to giving back to families in my hometown, putting smiles on kids’ faces and helping them start the school year on the right note with the right supplies."

And, get this ... we're told Meek's gonna surprise some kids Wednesday to personally hand-deliver the loot. Little advice for him though -- do NOT wear a Santa hat! That's risky biz in Philly.