just out of curiosity, I tried to find a listing of states that have separate organizations for public and private schools.
as near as I can tell, according to the National Federation Of State High School Associations:
there are 12 states that have more than one governing body for HS sports and activities. This includes Iowa, which has separate organizations running Boys and Girls sports.
Alabama, Georgia, Mississippi and South Carolina have "Independent" school associations along with public school associations. This goes back to segregation when schools split along racial lines.
Pennsylvania has an Independent school association with 24 schools. Oklahoma has a Christian Athletic association with 54 schools.
states that have public and private school associations:
Texas has 4 separate organizations for private schools.
Virginia, North Carolina and Maryland all have separate organizations for private schools. In Virginia and North Carolina, private schools are allowed to join the public school associations if they meet certain criteria, such as agreeing they will not offer scholarships or recruit athletes.
New York has a different setup (too long to get into), but they do have a Catholic School athletic association.
within the other 38 states, private schools are part of the overall HS association. some states do use multipliers and other systems for assigning private schools to athletic classifications.