1. IXL Personalized Learning
I like this source because it has K-12 Curriculum. It is aligned wth TEKS. It covers multiple disciplines.
This source has adaptive learning and multi-player games. It is Aligned to all major curricula.
3. Khan Academy
This is a free learning source available to everyone around the world.
This is a source with educational games.
5. PBS kids
This is a source with activities, videos, and educational games. It covers multiple subject areas.