In discussions about Portland Public School foundations I sometimes see this assertion. Often it's part of a broader critique of foundations and their impact on equity. The claim is that foundations don't just increase inequity, but actively harm students in other neighborhoods because parents in "semi-privatized" communities don't support public taxes.
For kicks, I got shape files and a vote abstract from Multnomah County and charted it. Below is a heat chart for 2011's measure 26-122. This is a property tax levy specific to Portland Public Schools, it passed with 58% of the vote. The red indicates low support and green indicates high. The labeling is based on decimals, 0.5 = 50% to 60%, 0.4 = 40% to 50%, etc.
I've marked with red dots the rough location of the top 4 elementary schools and K-8's based on fundraising. What do I see?
I see 3 of the 4 schools are located in precincts where the levy passed, and are surrounded by precincts with similar support. I also see a vivid geographic pattern: the inner city neighborhoods supported the levy more than outer neighborhoods. This pattern dominates the story of which precincts supported the levy and which did not, I don't see any correlation with the location of a high-foundation school.
Below is the same chart for 2010's measure 66, a statewide tax increase. Same thing: