A former labmate that I did my PhD with is now an engineering postdoc in Switzerland. Apparently, if you fail an undergraduate engineering exam in Switzerland, you get to re-write it once. If you fail it a second time, you are banned from practicing engineering in the whole country for life. One of his first teaching assignments was to write and grade one question for the re-take exam for a second-year dynamics class.

He had students that were asking him what Newton's third law was during the exam. Those students probably failed and are now banned from practicing engineering. He told me his guilt was relieved slightly when he realized the system was in place primarily to save lives. The re-take exam was more than fair; his question could have been passed with high school physics. Moreover, the exam was open-book. At some point students need to realize that this serious, and if you want a career in something that is going to affect the safety and well-being of a lot of people, then you cannot do a substandard job.