When Is Philosophy Appropriate?

There was an interesting discussion over at The Nonsequitur, one of my favorite blogs out there, a couple weeks ago about teaching philosophy before college. Certainly, it is not a good thing that we wait until university-level education to begin people -- those few who elect to take it --thinking about foundational questions. If we want a more reflective, thoughtful culture, surely it is a good idea to incorporate philosophy into regular curricula so that students get both exposure and training in deep thought.

I think two of the reasons it is not taught earlier is that we see secondary education, especially in this test-crazy era, as vo-tech training for middle management jobs. We are preparing students for the work force, not creating interesting, interested citizens with round and lively minds. Second, schooling is as much about keeping order as it is educating and arming students with the ability to challenge their teachers, parents, and what's being taught by both is threatening.

Of course, these are actually reasons why philosophy should be taught, but the question is at what age? When should children ideally begin their philosophical education. Plato, of course, argued that children shouldn't be educated in this way, that we need to wait for a mature brain. Developmental psychology paints a picture of a brain that develops in stages, starting more concrete and advancing towards abstract concepts. To make this anecdotal, when did you start being philosophical? When in your own development would it have been effective to introduce you to the world of philosophy?