Last night I was "helping" DD8 with some WWII-related online research. In this case, "helping" basically meant doing the research myself, then breaking it down into chunks small enough for an 8yo to digest. If you compared the content of her school-provided textbooks and research supplements with a garden-variety Wikipedia page, there's 10x more content and complexity online.
I'd much rather give her the tools to do it herself, and then let her do it herself. Anyone have any age-appropriate, online encyclopedias they can recommend?