Edible marijuana products are pictured on display at a medical marijuana dispensary in Denver on April 18. Many of the items are far more potent than a single marijuana joint. Two recent deaths have raised concerns about Colorado’s recreational marijuana industry and the effects of the drug, especially since cookies, candy and other pot edibles can be more potent than a smoked joint. (AP Photo/Ed Andrieski)

A couple of 10-year-old Colorado kids were caught making marijuana deals at school — selling and swapping legally purchased pot they pilfered from their grandparents’ stash, a school district official said Wednesday.

A fourth-grade boy brought a small amount of leafy marijuana on Monday to Monfort Elementary School in Greeley, Colo., and sold it to three classmates on the school playground. He made $11 on the deal, John Gates, director of safety and security for Greeley-Evans School District, told ABC News.

The next day, one of the buyers brought an edible to school and gave it to the boy who sold him the weed.

One student admitted to taking a small bite of the edible but a medical exam did not indicate any harm.

Voters in Colorado approved the possession and use of small amounts of cannabis by adults for recreational purposes in 2012, and the first state-licensed retail pot stores opened in the state in January.

The marijuana was reportedly purchased by grandparents in two different families, Gates told CBS News.

Another student, who was not a participant in the activity, observed the incident and reported it to school authorities. Gates said the district has disciplined the four fourth-graders — three boys and a girl — but did not elaborate. He also said that no charges are expected to be filed in connection with the incident.

Jennifer Sheldon, principal of Monfort Elementary, sent a letter home to parents informing them of the incidents and noting that “disciplinary action is underway” for the involved students, Reuters reported.

“We urge all parents, grandparents and anyone who cares for children to treat marijuana as you would prescription drugs, alcohol, or even firearms,” the letter stated. “This drug is potentially lethal to children and should always be kept under lock and key, away from young people.”