Our's is similar, about 500 schools, but not everyone makes the playoffs. Usually it's top half of each league will qualify. Single elimination -- have to win 5 (or 6 if low seed). Public and privates together. Seven classifications (Division 1, Division 2, etc.) -- but it's like English soccer: finish at or near the bottom of your division and you're moved down to a lower division next year; finish at or near the top and you're moved up. The net result is that the higher divisions are really strong, with the overwhelming majority of the top teams. That said, the team that won Division 3 this year was darn good, and will see themselves in Division 2 next year.