I understand the issue, it is difficult to find good examples where using boolean operators makes a clear improvement to results. With my groups I started with some physical assessment of their own understanding of logical statements AND OR NOT etc. e.g Stand up if you are a girl AND in the back row, stand up if you are in row 1 AND row 2, we found that it was a common misconception that you could easily be in both rows, we finished on a Not statement! As we had watched the april fools from the BBC about flying penguins in a previous lesson they then used advanced search to show "flying penguins" finds a lot of offical looking websites with the content but "flying penguins" -"April fool" drops nearly all of these out of the results. Another useful feature is that clicking the cached website in google search results actually highlights the found search terms in yellow (though those cached sites were filtered at school so a screenshot was used). From our T1 and Inital Levelling tests, advanced search and boolean seem to be some of the weakest areas for KS3. I'd also say the job of teaching accurate use of the web for finding and evaluating information is a major task, but it can be more fun that identifying top level domains, many of which can be registered by anyone with about £7 to spare!