Working with human beings changes the rules. If we start there, we end up with multiple choice exams that measure factual knowledge or memorization or test-taking skill. With people, and especially when the goals are understanding and attitudes, it's much more complicated. Fortunately, there's are professional evaluators who make their living assessing the success of programs and other efforts. Unfortunately, not all our efforts are at a level where we can hire someone.
Assessment is still important, even on a small scale.
It can sometimes be done as part of the process . Sometimes accomplishment of a stage of an activity can be a quick evaluation of understanding. Sometimes they surprise me. Although I said this was about assessing the program, not the student, we do sometimes need to assess the students individually. In that situation, too, it's important to assess what you value .