(Proverbs 27:22 KJV) Though thou shouldest bray a fool in a mortar among wheat with a pestle, yet will not his foolishness depart from him.
Have you ever tried to use a mortar and pestle on something hard to grind? I tried it on coffee beans once and decided that some things have gotten better with progress. Coffee can be ground with this method but it takes a long time. My guess is that the slaves were put on the task in ancient times and were beaten if it did not come out fine enough. You need that kind of motivation to make it work. If the guy drinking the coffee was forced to grind it I think that coffee would have never become a popular beverage.
We need to take that lesson to heart when it comes to working with fools. Can they be helped? Maybe. This verse would make it sound impossible. It seems to say “once a fool, always a fool”. But just as grain or coffee can be eventually ground down, so might a fool. It might take longer than they have to live and it certainly will take more energy than you have to give, but it might happen.
So? Learn to recognize fools. They come in all shapes and sizes. They cover the entire spectrum of the IQ scale. It might be that the only way you can find out for sure is to talk about real wisdom and see how they respond. Keep in mind that even Jesus was rejected by the multitudes.