"Of those who responded to the survey, 40 percent of those in the U.S. House of Representatives who have school-aged children, and 49 percent of those in the Senate who have school-aged children, send or have sent at least one of their children to private school.", source: Heritage Foundation
That organization has an agenda to represent the position of so-called "school choice", so I think if anything they would pump the numbers up higher for private school (kind of already have in the phrasing: "at least one of").
That said, I'm willing to accept that 41% of Senators use public school exclusively. That seems realistic. For politicians at the state and local level, it's going to vary far more than a small group that lives in D.C.
I know of some local politicians who have kids in the public school system. But I live (or used to live) in the SF Bay Area, which has several good public schools and many bad ones. Live near a good school, then why wouldn't you send your kids there. If you paid a premium to live in Cupertino, part of that is because it is desirable for its school district (Monta Vista, etc).