Here is my old answer, based on true life experiences in NYC back in the bad old days of the 1070s: A liberal is a person who will lobby the government to institute bussing to intergrate the public schools, and then send their own children to private school.
I suppose this could be easily updated with a charter school reference. More precisely these people would be called "limosine liberals", but lately it seems like they are all of that ilk. Maybe that phrase needs updating too, Al Gore in an SUV liberals, or something like that.
I bow to your vast experience. What are your thoughts on the new Archbishop of Canterbury?