Construction of Brentwood, named for the new housing sub-division being built in the area, began in July 1962. The school opened for student enrollment in November 1963 as an elementary school. The building was one large circle with another smaller circle stacked on top. Inside the original building were 12 classrooms on the ground level with the library in the center of the circle. The upper level housed a kindergarten room, cafeteria, mechanical room, and office. The building had a covered play area and entry way. Eventually, a separate gymnasium was added.
In June 1975, Brentwood became a middle school with the addition of locker rooms, three classrooms, kitchen, larger cafeteria, and library. The elective hall was added in 1988 which created a band room, choir room, art rooms, and new restrooms for Brentwood's growing population. Two portable buildings were also moved to Brentwood in this interval. In 1998, the west wing was added to accommodate eight new classrooms and restrooms on two levels, one for sixth grade and one for eighth grade. At this time, the office and student health room also underwent extensive changes.
In 2002, Brentwood acquired a new gymnasium converting the exisiting gymnasium to a fitness room, boys' and girls' locker rooms, coaches' office, storage rooms, and one classroom. An additional portable building was acquired, and conversion of the two largest portables into a consumer and family studies classroom and an industrial arts shop took place during the summer of 2004.