ABCya.com was created by a teacher in answer to his quest for high quality online learning games. ABCya.com is an ad-supported site (but has a subscription option for removing any unwanted ads).
All of the educational games are free to play on PCs and modeled after lesson plans for each grade, from Kindergarten through 5th grade. Their mobile device games are not free and a subscription is needed there, but I understand there are six free mobile games each week.
Visit ABCya.com to look through their free learning games for elementary kids, sorted by grade.
Want other free learning games for kids? Look at this page I created just for kids: free online activities and games. I think you’ll find a new favorite there!