In addition to the sites we visit regularly, here are some others you might want to access.
MATH Specific
mathgames.comkhanacademy.org (for help)
virtualnerd.com (for help)
SCIENCE Specific
mysterydoug.com
https://www.exploratorium.edu/learn
https://www.exploratorium.edu/explore/activities
https://spaceplace.nasa.gov/
https://www.nasa.gov/kidsclub/index.html
https://kids.nationalgeographic.com/
Great selection of reading/activities
https://www.scholastic.com/learnathome