I've seen a few variations on this that are less blatant but equally effective at gaming the system. Note that these all happened in college, rather than in HS--I never recall seeing this in high school.
The first is professors providing previous exams for students to study from, and then only changing the numbers, not the questions (e.g. the test is a template). This wasn't the norm, but it wasn't uncommon either--several professors gained nicknames to this effect, and you knew if you were in one of their classes how everything was going to work.
Even if the professor didn't provide the exam, fraternities and sororities usually kept prior exams from folks who had done well, and I believe the "learning center" also would keep copies, to the point where I am occasionally recognized when I come back to campus (mostly for recruiting) because one of my completed computer architecture tests has been given out as reference for the past decade.
The second is providing study sessions the day/night before an exam where professors would run through common scenarios that might appear on tests. When done correctly, students would ask the questions and the prof would get another student to demonstrate and they would help as necessary--when done poorly (and unfortunately, in my experience, the more common of the two), it devolved to the first scenario.
Neither are explicitly "cheating" in the way outlined in the parent (I don't know if they'd show up on accreditation, for instance), but they achieve the same end result.
As a bonus, I worked as a proctor in the learning center for a year or two, and while the majority of students came in because they were legitimately struggling with one concept and needed tutoring to jump the knowledge gap, there was a core group of frequent fliers who were there every day basically getting their homework done by others, and thus boosting overall grades (and ultimately graduation rate).
As has been stated many, many times in this thread, incentives (staying accredited, getting some arbitrary US News and World Reports ranking, having a high graduation/job placement rate, etc.) push this behavior to the detriment of student learning.