The purpose of an educational institution is to provide an individual with the educational foundation to be able to sustain a healthy and productive life. Good decision making skills should be well promoted within the educational realm. After all, with knowledge comes responsibility, and they have the responsibility to themselves to make wise and sound decisions.
No, schools should not teach decision making. The danger of schools teaching decision making is that students will become indoctrinated and that students will not develop individual critical thinking skills. The best way of learning decision making is in fact my making mistakes. Attempting to teach decision making will actually weaken students ability to think as individuals. Additionally, it will compromise the concept of self by encouraging conformity to imposed perspectives.