Common Sense Education https://www.commonsense.org/education/top-picks/most-reliable-and-credible-sources-for-students
Virtual Learning Resources Center http://www.virtuallrc.com/

Kiddle
Kiddle

Britannica School Database https://school.eb.com/levels
National Geographic Kids https://kids.nationalgeographic.com
San Diego Zoo Kids - Animals https://sdzwildlifeexplorers.org/animals
Sweet Search http://www.sweetsearch.com/ 

Infotopia
http://www.infotopia.info/

Atlapedia
http://www.atlapedia.com/

Fact Monster
http://www.factmonster.com

Infotrek
https://infotrek.info/