I'm sorry, you're about to report a woman because you assume she can't afford the school and doesn't live in the district? Do you have any proof? Why on earth would you butt in at all?
And everything in your post reminds me of how desperately awful school finances are handled in the US - how dare a whole district be obviously better because the parents can afford higher taxes? How dare other children be given less of a chance at a public school because families are lower income? How on earth is that equal? ?
And how dare another mother, who snobbishly points out that a woman cannot (in her own mind) afford to live in a district, try to bar another child from what is seen as obviously a better education, again, at a public school? Infuriating.
If you don't like the system, there are ways to work to change it. Proper channels.
Breaking the rules just because you* find them unjust is not the solution. Neither is gossip.
The OP is asking about her social obligations while following the proper channels - she wants to take herself out
of the gossip ring and put the issue into the hands of those deemed in charge of the situation. That is the absolute right way to solve things. She should not be attacked for it.
If you have a problem with how things are run in your county, city, state or country, I absolutely urge you to join with your neighbors, speak up, write to politicians, make yourself heard and propose better ideas and methods. I know in my community, my local Civic Association has to beg
people to get involved, even though we fight hard for the betterment of our schools. We'd be thrilled to have more people, passionate people, get involved!
* general "you"