The high school was originally designed for three grades (10 through 12) and approximately 1,200 students. The main building was constructed in 1966, and the Collins Center was added in 1983.
By 1994-95, enrollment had already grown to 1,270 students in grades 9 through 12. The high school was partially renovated in 1995 to accommodate the addition of grade 9 and an enrollment of up to 1,500 students. That renovation included the addition of a science wing at the rear of the school, a new entrance and art classrooms, a field house, an expanded gym and an expanded cafeteria. The Collins Center and field house are large structures and are used extensively by the community, leaving the space available for school programs less than the total square footage implies.
Based on current space guidelines, the capacity of Andover High is approximately 1,400 students. Meanwhile, current enrollment is just under 1,800 with a projected increase to 1,900 over the next twenty years.