A lot to Tennessee counties have closed or rather consolidated high schools and middle schools into mega middle and high schools. My guess is this being Hamilton County {same county as Chattanooga} the census in the school is a result of this. In many counties what was a community high school a few years ago under the mega high school consolidation serves two or more previous high schools and the same with the Middle Schools. Hamilton County likely runs the school rather than the city.
It is a Hamilton County School according to the website. Run you cursor over the listing
that says schools and scroll down for a complete listing of high schools.