The county is planning to pay $8 million for an elementary school site directly across Goodwin Road from East Brainerd Elementary School.
Officials said East Brainerd and other elementaries in that area are at capacity.
The property at the former Cigna headquarters includes 18.6 acres and the 100,000-square-foot Cigna office building as well as parking areas.
Justin Witt of the county schools said it basically will require partitioning the large open space for classrooms and other school use. He said converting the office into a school is estimated at $15 million.
Officials said that still is a bargain considering building a brand new school from the ground up and acquiring the land might be $55 million.
The purchase will be from Empire Communities, which is buying the property from Cigna.
The entire site is 98 acres. The remainder will be residential, including a senior living section.
The school is expected to serve about 750 students.