Alrighty, I’m stumped again on what I thought would be an easy find (I even think this one may have come up on Kindertrauma once before, but I’ll be damned if I can find it seaching through your archives!)
It was an episode of some anthology TV series from the mid-80s(?) I want to say the show was associated with a known sci-fi writer like Arthur C. Clarke or Isaac Asimov, but can’t be sure (at first I thought it might be an episode of Ray Bradbury Theater but it doesn’t appear to be.)
The episode is set in a boarding school for children, set in the future and possibly on another planet. The planet is cloudy and rainy all the time and the sun only shines once every several years and then only for a few hours, and it is about to do so again in the next few days and everyone is excited about it. The teacher hands out “sun kits” to the class, containing sun screen, protective glasses, etc. in anticipation of the big event.
The day the sun finally shines, the kids gang up on one of the newer kids and lock her in a windowless classroom. The sun shines for the brief moment and all these flowers start blooming all around the school. It is over as quickly as it began and everything is cloudy again. The girl is let out of the classroom and she is crying at having missed the sun. The kids feel guilty and bring her armfulls of flowers.