When I was in 6th grade we read a short story (I'm pretty sure it was a short story) about Earth being conquered by aliens and they won't let the humans use electricity or cars. I don't remember much besides that but I'm pretty sure there were no turtle aliens in it. (It's not "The Singers Of Time".)
There was also a story about an alien family that was made out of sugar and they wouldn't let their kids out of the house in case it rained.
And an alien planet where the sun only come out for five minutes every 20 years or something and a girl from Earth would tell stories about the sun and flowers and the other kids locked her in a room so she couldn't see it.
I don't know if these were all part of the same book or if we just read a lot of sci-fi stories.