OKLAHOMA CITY -- A grandmother helped bust an alleged drug ring at an Oklahoma City elementary school, police said.

Police arrested a 12-year-old boy after the Eisenhower Elementary school principal found a bag of marijuana in his backpack. A grandmother tipped off the principal about drug activity at the school.

"A grandparent of one of the students became concerned when she saw text messages on her grandson's phone. These texts involved purchasing and selling marijuana," said Oklahoma City Police Sgt. Jennifer Wardlow.

Police also found a second bag of marijuana in the gym.

The school said the student is being disciplined and the school is setting up anti-bullying and anti-drug classes for students and parents.