In the advanced search, you can choose basic, intermediate and advanced reading results for your search. The "advanced search" option is located to the right of the search box.
This new option offers teachers more options for teaching search skills and helping students find appropriate sites for research projects. I shared the option at an elementary school today and the teachers felt that it would help them find resources for students that they could read and that they could use in their lessons. There are additional features in the advanced search that allow you to delineate the file format in a search. This is another way to narrow your search and can yield more of what you are searching for.