THE ARREST of a Montgomery County music teacher for allegedly possessing child pornography has prompted the question of whether warning signs went undetected or ignored. The criminal case against the teacher is likely to provide some answers, but it’s important that Montgomery school officials conduct their own investigation to determine whether procedures were properly followed or if safeguards need to be tightened.

Lawrence Joynes, a teacher at New Hampshire Estates Elementary School in Silver Spring, was arrested by Baltimore County authorities after a search of his Dundalk home allegedly resulted in the discovery of child pornography on his laptop computer. Since the Feb. 27 arrest, there has been concern among parents of New Hampshire Estates students that their children may have been victimized. There have been no charges to that effect but, The Post’s Donna St. George and Dan Morse reported last week, police said that some of what they described as inappropriate images confiscated from Mr. Joynes were taken inside the school. The attorney for Mr. Joynes did not return a call for comment.

Should alarm bells about the teacher’s behavior have prompted earlier action? Some parents and teachers said they had complained about Mr. Joynes keeping his classroom door locked, for instance, and tickling and hugging students. Such actions don’t necessarily indicate wrongdoing, and officials must resist a rush to judgment that can lead to wrongful accusations, as was the case three years ago with a Fairfax County teacher. But we have to wonder whether Montgomery school officials have sufficient systems in place to detect and deal with possible patterns of behavior.

This, unfortunately, is not the first instance in which the Montgomery bureaucracy has been accused of obliviousness in dealing with potential problems. The Maryland State Board of Education last year roundly criticized the district’s handling of the case of a former teacher, Daniel J. Picca, who was repeatedly warned and disciplined for questionable contact with students, mostly young boys, but kept his job for 17 years while being moved from school to school. (Mr. Picca was not charged with a crime and has denied any wrongdoing.) In upholding Mr. Picca’s eventual dismissal, the state board directed school systems to scour their personnel files and policies to ensure student safety; that admonition has been given new urgency by Mr. Joynes’s case.