Of particular interest is their section on specially targeted search engines for students:
Sweet Search, “a search engine for students,” provides resources and highlights key words in the search results. For emerging learners, consider using SweetSearch4Me, a search engine providing age-appropriate results and easy navigation. Other search engines ideal for emerging learners include PrimarySchoolICT and KidRex, both powered by Google Custom Search. Articles, multimedia and video clips can be found in resources such as Discovery Education, the content repository within Project Share, and the archives of Popular Science.
Teachers often ask me for suggestions for search engines beyond the scope of Google. Drive around on the pages of the preceding search engines and consider adding one or more of them to your Problem-Based Learning experiences for your students.