"Judgments are prepared for scoffers and blows for the back of fools"
It is unclear whether the writer is suggesting that those who are scoffers need their discipline and training to be much more planned out or they will not get it, or whether God is preparing special training sessions for the scoffer. So often the cynical person does not see the truth because their angle at the truth is too oblique.
The idea that blows are for the back of fools is clearly suggesting that those who are impulsive and selfish and rebellious must be corrected. They cannot be allowed to just continue on as though there were no consequences for their foolishness.
This is a powerful warning to parents. You cannot just assume that your children's rebellious expressions of independence will be outgrown. You must train; you must correct; you must work when your teen or pre-teen is selfish, impulsive, and rebellious.