ABC Mouse: (Paid Subscription required) A great learning platform for little ones. My son used it from 2-7 years old and my daughter is currently using it. There is a learning path the kids can follow but also a classroom environment where they can choose many different subjects to play games, do puzzles, art, listen to books (read along), read books and watch videos.

Adventure Academy: (Paid Subscription required) Made by creators of ABC Mouse as well but geared towards kids 8-13. I found some of the lessons lacking in this one, especially for older kids but the environment, UX is incredible. An animated 3D world that allows kids to explore school grounds and surrounding areas and learn new things in each room/location.

Khan Academy/Khan Academy Kids: (Free) Kids' version is geared towards 2-8 years old and main version is geared towards everyone. A definite go to learning resource with lessons on pretty much everything. The kids one isn't as good as ABC Mouse in my opinion but it is still really good and it's free. My son loves using the main Khan Academy as a pseudo tutor. If he learned something in math that he needs a further grasp of he will use Khan Academy videos to help him along.

Tynker/Tynker Jr: (Paid Subscription required) Good and fun coding platform for kids. They get to code games using tynker designed code block language but can also advance to popular programming languages like python and java script.

Scratch/Scratch Jr: (Free) A good alternative for code block coding if you don't want to pay. My daughter really likes Scratch Jr and Scratch is good as well but I have found at least with my son he spends more time on Scratch playing other people's games than actually building and learning.

Synthesis: (Paid subscription) My son has been doing Synthesis for a couple years. This is the learning/critical thinking platform developed by the teacher that used to tutor Elon's kids. It's for kids 8-14. The kids form teams and play various games that challenge their ability to solve problems cooperatively. It's great but the amount of games is limited. The games do change and goals, teams etc change as well but I have found once the kids know the ins and outs of the games it doesn't provide as much value as when they are fumbling their way through at the beginning. They also have a math tutor platform which is good but only goes up to ages 11. I believe they plan to expand this offering.

Biochemistry Literacy for Kids: (Paid subscription) My son did this program a couple years ago and really enjoyed it. It's meant to teach college level Biochemistry in a basic form