I remember how adults used to dumb things down for me or simply ignore me on matters they thought "a kid wouldn't understand", that's why I have a simple policy when talking with children/teenagers: treat them as if they're at the same level as me intelligence-wise.

Sadly, so far in my experience, most children are pretty dumb, for lack of a better word :-). That's why people underestimate them by default, never giving a chance to those who are indeed just as smart as many adults...