Part of the problem may be that you are looking for Middle Schools -- parochial schools in the Diocese of St. Petersburg don't use that system. You'll need to choose a grade school, as they teach K-8, and schools are mostly aligned with a parish (or group of parishes, if they need to band together to gather enough students; common these days as Catholics have smaller families.)
The full list is on the Diocesan Education Dept. webpage.
http://home.catholicweb.com/dosp_ocsc/index.cfm
As with public schools, the Diocese will direct you to your local school based on where your home will be. However, it appears that there is an independent grade school in that diocese as well: Villa Madonna in Tampa, which is run by the Salesians. (While you don't have to use the school that is most closely affiliated with your parish, there is normally a tuition break for registered parishioners that nonmembers do not get.)
The key in evaluating a Parochial grade school, other than in the usual ways such as curriculum, test scores, and available resources, is to ask about two factors over time: how much their enrollment has varied over the past decade, and how much tuition has increased over the same period. Unless the school was consolidated in that time (in which case you should look at the numbers for the feeder parish schools), a wide pattern of negative change there can indicate a school that is struggling to stay afloat. Also, check the local newspaper; if schools are in trouble or outstanding they will be written about.
The only parochial school I know a little something about secondhand is St. Cecelia in Clearwater. A former client of mine sent her kids there and was quite happy with the school; it has a good reputation for math.