High Quality Content by WIKIPEDIA articles! William Mason High School, also known as Mason High School, (MHS) is a four-year public high school located in the Mason City School District in Mason, Ohio, a suburb of Cincinnati, Ohio. It serves more than 3,000 students in grades 9 through 12, supported by classroom teachers, media specialists, technologists, administrators, counselors and an array of staff members, special educators, volunteers and aides.