Unweaving the Rainbow | 0:16: Varying the refractive index of water. Short enough for the classroom.
The Greatest Double Rainbow | 0:27: A good double rainbow. Short enough for the classroom.
full circle rainbow | 0:28: You do NOT often see full-circle rainbows from the ground. In the video, the ground is a very high building. You can see full-circle rainbows from airplanes, but that may NOT be very common. People often see glories (rainbow-like full circles) from airplanes, but they are NOT rainbows: they are caused by a combination of refraction AND interference effects in water droplets. A glory has a smaller angular diameter measured from the solar optical axis than a rainbow. Short enough for the classroom.
How to simply make good rainbows in garden | 1:27: You can make your own rainbow with a garden hose. A few seconds is OK for the classroom.
triple rainbow | 0:18: A triple rainbow. I don't think this is an example of a supernumeray rainbow. Short enough for the classroom.
Rare Rainbow Cloud Phenomena known as a Circumhorizontal Arc | 0:33: This is probably a circumhorizontal arc which is ice crystal phenomenon and NOT a raindrop phenomenon like rainbows. Short enough for the classroom.
How a Rainbow Works | 3:17: Too long for the classroom.
Regenbogen | 2:22: The musical. See the second version Wenn's zum Regenbogen geht | 2:39 with lyrics---in German. The singer is Annett Louisan (1977--). Too long for classroom.