Old Mill Senior High School is an American public high school in Millersville, Maryland serving students in grades 9 through 12. It was occupied in 1975 and is administered by Anne Arundel County Public Schools (AACPS). The school was built to alleviate over-crowding at Arundel and Severna Park High Schools. Along with Annapolis High School and Meade Senior High School, Old Mill Senior High is one of the three IB World Schools in Anne Arundel County.