which uses "The local school official in charge of discipline"
http://policy.cps.k12.il.us/documents/705.5.pdfand from the Bureau of Labor Statistics:
"Assistant principals aid the principal in the overall administration of the school. Some assistant principals hold the position for only a few years, during which time they prepare for advancement to principal; others are assistant principals throughout their careers. They are primarily responsible for scheduling student classes and ordering textbooks and supplies. They also coordinate transportation, custodial, cafeteria, and other support services. They usually handle student discipline and attendance problems, social and recreational programs, and matters of health and safety."
http://www.bls.gov/oco/ocos007.htm