The northern boundary for Southern Middle is the southern boundary of for Calvert Middle School.

The southern boundary begins at the Patuxent River and moves up St. Leonard Creek to Rollins Cove. At this point the line turns easterly to the intersection of Pardoe Road and Rte. 4. The line turns south and follows on the east side of Rte. 4 and the west side of H.G.Trueman Rd. to the western entrance to the Chesapeake Ranch Estates. The line enters Lake Lariat and moves in an easterly direction south of Sidewinder Rd. and Big Sandy Run Rd. to the back gate and east along Little Cove Point Rd. to Cobb Creek to the Bay.

The western boundary is the Patuxent River and the eastern boundary is the Chesapeake Bay.

The following communities and/or roads are included in Southern Middle School: Mackall Rd. south of the intersection of Ross Rd., Parran Rd., Calvert Beach, Long Beach, White Sands, Cove Point Rd., Little Cove Point Rd., the northeast section of the Chesapeake Ranch Estates. The line enters by the Texaco Station moving north of Geronimo Road to Lake Lariat and turns east in Lake Lariat south of Deadwood Drive to the Bay, south of Big Sandy.