Please don't post pictures showing the media player window. Most players have built in functionality to take a snapshot of the video frame (menu option and/or hotkey, shift+s in VLC and you can also use the e key to step a frame forward).

I'm not sure what kind of answer you expect, do you mean within Love Live or anime in general? Sorting the idol tag in AniDB to display the oldest first I find Idol Boueitai Hummingbird from 1993 on the second page which comes close or at least may be a title to include in an answer, if I didn't get your question wrong. (I haven't watched this, it says military, so it doesn't actually qualify as a school setting.)

@Ikaros you shouldn't be too concerned about the hairstyle, this is the show where the protagonists reappear with completely different outfits, hairstyles and eye colors. :)

@Maroon I have only watched the first episode until now and it looks like they want to make it as accessible for everyone as possible, building up the background that leads to the original series but at the cost of one spoiler in the original series. If that's fine with you then it should be okay. Regarding context of politics and technology my expectation is that the series will hopefully be easy to follow and comprehend.

Your UC does not appear to be in order, for example according to another page in the wiki 8th MS Team is UC0079 and far away from Unicorn in UC0096. I would also add The Origin and probably Gundam Reconguista in G to UC. There are also the Advanced Generation and Post Disaster (and Correct Century¿?) timelines, which you probably have missed. The page is really long. :\