An elementary school principal was released without bail Friday after pleading innocent to drug charges, and school officials questioned a system that protected him for 16 years despite a troubled history.

Matthew Barnwell, 55, was freed on his own recognizance after pleading innocent to a misdemeanor charge of criminal possession of a controlled substance during arraignment in Criminal Court.Barnwell, the first city principal ever arrested on drug charges, is to return to court Nov. 22.

His arrest Wednesday for allegedly buying two vials of crack on a Harlem street corner has sparked a review of the process that kept him on the job despite complaints about job performance, drinking and drug use.