Is it right to say: "Lazy students aren't worth of free education" or "Lazy students aren't worth free education"?
Lazy students aren't worth of free education
doesn't mean anything to me.
If I heard
- Lazy students aren't worth free education
from a native speaker, then I would understand it to mean
- Lazy student are not worthy of a free education
- It is not worth the effort to give lazy students free education.
So, in my opinion, if your goal was to try to sound like a native speaker and you used 1., then congratulations, I think you did a fine job. In fact, I would probably say 1.
If this was not your goal, then try to rephrase 1. to convey your true meaning.