So taking something like "1984 is a political novel written with the purpose of warning readers in the West of the dangers of totalitarian government." (topic sentence of sparknotes)
but instead writing something, off the top of my head, like "Totalitarian government can be seen to be focused upon in George Orwell's political novel 1984 with the purpose of warning readers in the West of its potential for oppression."
Surely something like that cannot be considered Plagarism. With thousands of kids doing English papers, you are going to have lots of people talking about pretty much the same thing, and even if you come up with something genuinely your own, im sure someone else out there will still have something as similar to your sentence as my improv sentence is to sparknotes.