Booster club at our current gym is optional and at the previous gym was "mandatory." Thing is folks, you cannot make anyone join an organization especially when this would mean incurring a financial obligation(ex. mandatory fundraisers, fee to join etc.) If a parent ever took it to court, the whole mandatory booster club thing would be deemed illegal---violates public policy, freedom of associaiton etc. Why do parents get sucked into this? They're not aware they have the right to say "no" and figure since its done this way, it must be ok, don't want to "rock the boat", fear of child getting caught in the middle etc. Your obligation is to pay for monthly tuition, leos etc. and meet/coaches fees-----to the gym. If that is done, then there is no legal way for your child to be kicked off team or whatever.
I was told our current booster club found this out----the hard way. They used to require all parents be members and all members had to work bingo. So, if your dd was on team, you were required to do bingo. One family said they had no problem with being in the booster club, but did not want to do bingo. They were told they had no choice. They got a lawyer who used the state gaming laws(which get rather complicated), but basically say people can't be forced to help in a gambling enterprise if they do not want to(bingo is gambling). Booster club was fined $25k by the state. End of ANY mandatory anything. Family is no longer involved with gymnastics, but they stood up for themselves and taught one booster club a lesson.