In Massachusetts you are only allowed to compete at 7 tournaments in a season, this includes your league, your regional and your state competition. All events must be sanctioned by the MSSAA (which are typically only instate, with the exception of a couple in Rhode Island). You must qualify at leagues for regionals and at regionals for states. At states they only give teams with a certain score or higher or the champions in the division the bid to go to Nationals.
So when you see Masschusetts teams at "nationals", they qualified to get there!
We have 2 seasons Fall and Winter and the same rules apply for both seasons.