The Danbury Public School District is using a new visitor registration system this year.   Information from government-issued IDs will be compared to a nationwide sex offender database before school staff can print a badge that allows a visitor to be admitted on school grounds.  Officials say Raptor will be a frontline defense against registered sex offenders and will be used each time a visitor, contractor or volunteer signs in, or a guardian signs out a student. District administrators say safety of all students is their highest priority and is working to improve on security measures.