The following websites are excellent resources that provide additional ways to reinforce and enrich the concepts that the children are studying at school.
EPGY Stanford Math and Stanford Language- http://epgy.stanford.edu/login/index.html
Discovery Education (Practice Probes)- http://www.discoveryeducation.com/students/index.cfm?campaign=flyout_students
Internet4Classrooms- http://www.internet4classrooms.com
Starfall.com- http://www.starfall.com
FunBrain- http://www.funbrain.com/
PBS Kids- http://pbskids.org