Denn John Middle School originated in the fall of 1974. It was housed on the Beaumont Middle School site until construction was completed and named “Kissimmee Middle School.” The first principal was John B. Hayes.
The school opened at its present site in January 1975 and the school board voted to rename it Denn John Middle School after two life-long citizens living on the street: Dr. Denning and Youel Johnston.
The school was built to house 1200 students, and since its opening has undergone several additions. In 1992, three buildings were built; currently, these buildings house the music and science departments. During the summer of 2002, a gymnasium was built with the assistance of Kissimmee Parks and Recreation. There are also 7 portable buildings on campus.