Hour of Code
Lots of options on Hour of Code.com
I recommend:
First Grade- Kodable
Second Grade- The Foos
Third Grade- Lightbot
Fourth Grade- Code.org - Minecraft Voyage Aquatic
Fifth Grade- Scratch Cartoon Network Adventure Game
Sixth Grade- Google Grasshopper
Other resources
Google Santa Tracker Codelab &
Santa Tracker Code Boogie (Only available in December, best for primary grades.)