Numberblocks on Netflix.

Slick Slime Sam on YouTube Kids

Agree with all the PBS recs on here, especially Dino Dan/Dana and Wild Kratts. 6.5yo likes Odd Squad, 4.5yo not as much. Original Magic School Bus episodes on Netflix -- I think it's better than the reboot.

My 6.5yo also really likes the vet and zookeeper reality shows on Nat Geo and Discovery+. I usually watch those with him and occasionally mute/skip parts because they sometimes show surgery or discuss animal death.

Also, How It's Made (I know it's on cable, not sure if you could find episodes on YouTube or something).

Anything on PBS Kids
We liked Peg + Cal and Odd Squad (may be a touch too old for the 5 yo)

Dino Dana and Dino Dan

Dino Dan/Dana and Wild Kratts were the top ones here. The Disney+ show about Animal Kingdom is also good. I don't think any animals died during that. Secrets of the Zoo is good but there is animal death, which can be hard for some kids that age. My kid could handle it once she hit 9. "Circle of Life mom" is what she'd say lol.

Do you let them watch shows for fun? If so, just change the language settings. They'll learn a foreign language

Puffin Rock, Waffles & Mochi, Ada Twist Scientist and StoryBots are big in our house. All Netflix.

Not explicitly educational in the same way as Wild Kratts or Word World, but Arthur. Also, Odd Squad which I appreciate for its weirdness and its math.

Both the old and new Magic School Bus are great.

My kindergartener likes Word World and my 2nd grader likes Magic School Bus (the newer one).

Wild Kratts, Xavier Riddle, and Let's Go Luna are all PBS Kids shows that are huge hits with my 6yo DD.

The Who Was Show on Netflix. My DS loved it and is still upset at 9 yo that there won't be a second season.

Zooboomafoo on amazon prime

My kids used to love Magic School Bus and i think it’s on Netflix now.

Octonauts