Gizmos

Gizmos are interactive online activities students can do independently or as a whole class.  Gizmos come with a teacher lesson plan as well as student activities and answer keys.  Gizmos relate to Math and Science and align with the K-12 curriculum, but the government is only providing them to K-6 teachers for free at this time.  

Explore Learning states they are 3-12 because you need grade 3 and up reading skills to engage in the Gizmos independently.  K-2 classes can do teacher-led activities and there are many curriculum-aligned Gizmos for this age group.