These are rehosted in their proper resolution from Disney's Education Productions section of their website:
It's odd that they just show you the video in the tiny player, you need to download the videos with the nifty DownloadHelper add-on for Firefox, it truly works, honest. :)
The following in the three parts is along with their resolutions:
In the Water (Entire) 624x352 16:9 About Fire (Entire) 432x242 16:9 At Home (Clip) 384x288 4:3 Goes Green (Clip) 320x240 4:3 (Actually in 16:9 but left in 4:3 for the sake of preserving it as was)
This is why the quality between the shows varies. :)
I had to put these all together and then split them in three since the first two in their entirety are over 10 minutes. :(
Would've saved me a huge headache if it wasn't for that rule. :/
Since these are from the website, there should not be any worry of Disney forcing YouTube to pull down these videos since they're showing them for free on their website in the first place!