No wonder our city schools are failing; they can’t keep their computers from being stolen.

A prowler lifted a dozen MacBooks — worth $12,000 — from the HS of Arts and Technology at Amsterdam Avenue and West 66th Street in Manhattan between 5:30 p.m. last Friday and 7:30 a.m. Monday, police sources said.

The intruder broke into an office, smashed a lock on a cart and took the computers.

A custodian was seen on video with a drill in an area not assigned to him, but he has not been charged.