An 11-year-old boy was busted Wednesday after he slashed a teenager’s face in Brooklyn, police said.

The knifing happened just after 9 a.m. near Uncommon Schools Leadership Prep — a charter school the boys attend.

The students were arguing on MacDonough Street between Marcy and Thompkins avenues when the 11-year-old pulled out a knife and slashed the 13-year-old boy, cops said.

The victim ran into the school for help. He was taken to Maimonides Medical Center, where he was listed in stable condition.

Charges against the 11-year-old were pending, police said.

According to law-enforcement sources, the boys had a fight over a football game from the day before.

Area residents were stunned by the young ages of those involved.

“Eleven years old? That’s too young. Why’d he have a knife?” one said.