An article called "Cashing In, Getting Extras" describes inequities in school fundraising in Chicago. But you could replace "Chicago" with "Seattle" througout the article and have a pretty accurate picture of what is happening here.
I'd like to explore the idea of pooled PTA fundraising, with some percentage of funds raised by each school put in a district-wide pool that is divided and sent back out to schools on a per-student basis. Palo Alto explored this option. Read "School-based fund-raising must be curbed" for one perspective on this issue.
And an article called "Can Parent Groups Do Too Much" raises additional interesting issues on this topic. When parents are paying teacher salaries and providing essential classroom materials, does that let the state off the hook for adequate funding of schools?
Offerings like art and foreign language, which are funded by parents, contribute to a public school system that provides unequal opportunities to children depending upon the wealth and fundraising abilities of parents at the school. That is clearly wrong.