It seems to me that kids will only be interested the the seemingly 'abstract' concepts of boolean operators when they are actively searching for information and frustrated with the results. At the point of frustration we have to be their with a lesson, or an on demand help system has to be a click a way, or the kid has to have a sense of optimistic persistence... or the teachable moment is lost.

It might be that fostering optimistic persistence is the best thing we can do.

The Question is HOW do we teach kids to be confident searchers when we spoon feed them resources and don't trust them to search during school hours? ~ Hiram