Related, there's no evidence that people behave more ethically after taking a course in ethics. But the education system has one hammer, teaching courses about subjects, so every problem looks like a nail. They want their students to behave ethically so for school systems there can be only one solution; they teach ethics courses.
It's likely that the true ethical education children receive is observing the behavior of people in their family and community from a very young age to learn what is or isn't acceptable. Schools can't do much about that, and if anything most modern schools are harmful in this regard because they generally award petty cheating and excuse spinning. And so too do schools teach the wrong approach to critical thinking and cognitive biases. Schools reward students for conforming to what their teachers say and give students trouble when they think on their own. This is particularly true during the youngest grades. Some high-concept courses about critical thinking in highschool won't undo the damage; by that time students already learned to either conform with authority or become equally unthinking reflexively contrarian rebels.
It's likely that the true ethical education children receive is observing the behavior of people in their family and community from a very young age to learn what is or isn't acceptable. Schools can't do much about that, and if anything most modern schools are harmful in this regard because they generally award petty cheating and excuse spinning. And so too do schools teach the wrong approach to critical thinking and cognitive biases. Schools reward students for conforming to what their teachers say and give students trouble when they think on their own. This is particularly true during the youngest grades. Some high-concept courses about critical thinking in highschool won't undo the damage; by that time students already learned to either conform with authority or become equally unthinking reflexively contrarian rebels.