Rehab is no frat house, a stern judge warned a former Columbia University anthropology student in giving him a treatment-not-jail deal today for admittedly selling pot by the pound out of the International House dorm.

“This is not a frat,” Manhattan Criminal Court Judge Ellen Coin warned Chris Coles, 21, in sending him to an Upper Manhattan inpatient treatment program.

“This is going to be a bunch of people with substance abuse issues and they come from all walks of life,” the judge told him. “Your job is to get through this program.”

Coles enters rehab after pleading guilty today to drug sales and possession; he was one of five students accused last winter of selling felony-weight quantities of cocaine, pot and pills out of dorms and frat houses at Columbia.

He had spent the last two weeks in jail after testing positive for pot use even while home awaiting his court-monitored treatment program, which, if completed successfully, will result in his record getting wiped clean.

Coles suffered from serious marijuana dependency and spent his school days “continually stoned,” his lawyer, Mark Agnifilo, had said in successfully asking for treatment in lieu of jail over the objection of narcotics prosecutors.

Of the five students charged, Coles is the only one with a judge’s approval for a program under which all charges will be dismissed upon the successful completion of treatment.