I say: "Students not studying will fail" as being equivalent to "Students who don't study will fail"
Is it wrong?
What about this too: "People not having to get up early don't have to sleep early" as being equivalent to "People who don't have to get up early don't have to sleep early"..
What do you say?
The sentence regarding getting up early is not natural. For a start, we usually say that people who have to get up early also have to "go to bed" or "go to sleep" early, not just "sleep". I can't really put my finger on why "People not having to" doesn't work here, it just doesn't, in my opinion.
One full stop is sufficient at the end of a sentence.