Most religious schools do not publish their statistics, but they will normally give them to you if you ask for them individually. Are you asking about high schools or grade schools? (There is a difference because grade schools are normally under parish control, whereas high schools are most commonly under the control of either the diocese or a private religious order.)
The most common place to find published numbers on private schools, I find, is a local business magazine or newspaper, since they tend to be read religiously by the parental demographic that those schools are looking for. Try this list:
http://www.palmbeachpost.com/hp/content/education/pbcpri_index.html