There are many search engines available. I suggest that elementary students only use those that are specifically kid safe/friendly and age content appropriate. Here are some recommendations from the Search Engine Watch experts to recommend to your students for projects or computer lab work.

Ask Jeeves For Kids             http://www.ajkids.com/
Ask Jeeves is a unique service where you enter a question in natural language.

Enchanted Learning       http://www.enchantedlearning.com
A site designed just for elementary students

KidsKonnect      http://www.kidskonnect.com

Internet public Library's Kid's Space   http://www.ipl.org/div/kidspace/
        
KidsClick!      http://www.kidsclick.org/
Backed by librarians, KidsClick lists about 5,000 web sites in various categories.

Looksmart's Kids Directory      http://search.netnanny.com/?pi=nnh3&ch=kids
The Kids Directory is a listing of over 20,000 kid friendly websites that were hand picked by employees of Looksmart subsidiary Net Nanny and vetted for quality.

Yahooligans     http://www.yahooligans.com/
Yahoo for kids, designed for ages 7 to 12. Sites are hand-picked to be appropriate for children.

ALA Great Web Site for Kid      http://www.ala.org/greatsites
An organized directory of sites selected by members of the American Library Association

Awesome Library         http://www.awesomelibrary.org/
Over 14,000 sites have been classified into a directory, specifically organized for teachers, students and parents

Diddabdoo       http://www.dibdabdoo.com/
Billed as an ad free, non-commercial directory of web sites designed for child-safe searching.

Fact Monster    http://www.factmonster.com/
Reference provider Information Please produces this site which provides facts and information oriented around the needs of children.

Family Source   http://www.family-source.com/
This focused crawler-based service has indexed nearly 1 million kid-friendly URLs.

FirstGov for Kids       http://www.kids.gov/
From the U.S. Federal Citizen Information Center, this directory provides links to government-related kids' sites along with some of the best kids' sites from other organizations, grouped by subject.

Kids Search Tools       http://www.rcls.org/ksearch.htm
Search a variety of kid-safe search engines from a single page.

SearchEdu.com   http://www.searchedu.com/
Index of pages built by crawling education web sites.

Teach-nology.com        http://www.teach-nology.com/
Directory of web sites for teachers and educators.

TekMom's Search Tools for Students      http://www.tekmom.com/search/
All-in-one search page for kid search sites and research resources.