[WS:] That does not strike me as very rich - it sounds pretty middle class, say a household of two school teachers, or two government employees, or a college prof and an office worker, etc. It is more appropriate to interpret it that the professional class prefers public education, which sociologically makes perfect sense.
The rich, which is a seven digit income +, most likely prefer private schools but they are very few of them, the 1% if you will, to make any difference in such statistics.
A related topic - playing a populist card in discussing education in the US is a sure way to end on the right wing side of the debate.
Wojtek