From the website:
SweetSearch is a Search Engine for Students.
It searches only the 35,000 Web sites that our staff of research experts and librarians and teachers have evaluated and approved when creating the content on findingDulcinea. We constantly evaluate our search results and “fine-tune” them, by increasing the ranking of Web sites from organizations such as the Library of Congress, the Smithsonian, PBS and university Web sites.
SweetSearch helps students find outstanding information, faster. It enables them to determine the most relevant results from a list of credible resources, and makes it much easier for them to find primary sources. We exclude not only the spam sites that many students could spot, but also the marginal sites that read well and authoritatively, but lack academic or journalistic rigor. As importantly, the very best Web sites that appear on the first page of SweetSearch results are often buried on other search engines.